微信小程序生成二维码（完美解决因链接过长报错问题）

    const QR = require('../../utils/weapp-qrcode.js')
    var imgData = QR.drawImg(this.data.codeText, {
      typeNumber: 4,
      errorCorrectLevel: 'M',
      size: 500
    })
    // 返回输出base64编码imgData

weapp-qrcode.js

//---------------------------------------------------------------------
//
// QR Code Generator for JavaScript
//
// Copyright (c) 2009 Kazuhiko Arase
//
// URL: http://www.d-project.com/
//
// Licensed under the MIT license:
//    http://www.opensource.org/licenses/mit-license.php
//
// The word 'QR Code' is registered trademark of
// DENSO WAVE INCORPORATED
//    http://www.denso-wave.com/qrcode/faqpatent-e.html
//
//---------------------------------------------------------------------

//---------------微信小程序基于base64生成二维码插件修改-------------------
/*
 * @Modified: Pudon
 * @demoURL: https://github.com/Pudon/weapp-qrcode
 * @Date: 2018-09-11 14:00:05 
 * @Last Modified by: Pudon
 * @Last Modified time: 2018-09-12 16:33:19
 */
//---------------------------------------------------------------------

/**
 * qrcode
 * @param typeNumber 1 to 40
 * @param errorCorrectLevel 'L','M','Q','H'
 */
var qrcode = function(typeNumber, errorCorrectLevel) {

    var PAD0 = 0xEC;
    var PAD1 = 0x11;

    var _typeNumber = typeNumber;
    var _errorCorrectLevel = QRErrorCorrectLevel[errorCorrectLevel];
    var _modules = null;
    var _moduleCount = 0;
    var _dataCache = null;
    var _dataList = new Array();

    var _this = {};

    var makeImpl = function(test, maskPattern) {

    _moduleCount = _typeNumber * 4 + 17;
    _modules = function(moduleCount) {
        var modules = new Array(moduleCount);
        for (var row = 0; row < moduleCount; row += 1) {
        modules[row] = new Array(moduleCount);
        for (var col = 0; col < moduleCount; col += 1) {
            modules[row][col] = null;
        }
        }
        return modules;
    }(_moduleCount);

    setupPositionProbePattern(0, 0);
    setupPositionProbePattern(_moduleCount - 7, 0);
    setupPositionProbePattern(0, _moduleCount - 7);
    setupPositionAdjustPattern();
    setupTimingPattern();
    setupTypeInfo(test, maskPattern);

    if (_typeNumber >= 7) {
        setupTypeNumber(test);
    }

    if (_dataCache == null) {
        _dataCache = createData(_typeNumber, _errorCorrectLevel, _dataList);
    }

    mapData(_dataCache, maskPattern);
    };

    var setupPositionProbePattern = function(row, col) {

    for (var r = -1; r <= 7; r += 1) {

        if (row + r <= -1 || _moduleCount <= row + r) continue;

        for (var c = -1; c <= 7; c += 1) {

        if (col + c <= -1 || _moduleCount <= col + c) continue;

        if ( (0 <= r && r <= 6 && (c == 0 || c == 6) )
             || (0 <= c && c <= 6 && (r == 0 || r == 6) )
             || (2 <= r && r <= 4 && 2 <= c && c <= 4) ) {
            _modules[row + r][col + c] = true;
        } else {
            _modules[row + r][col + c] = false;
        }
        }
    }
    };

    var getBestMaskPattern = function() {

    var minLostPoint = 0;
    var pattern = 0;

    for (var i = 0; i < 8; i += 1) {

        makeImpl(true, i);

        var lostPoint = QRUtil.getLostPoint(_this);

        if (i == 0 || minLostPoint > lostPoint) {
        minLostPoint = lostPoint;
        pattern = i;
        }
    }

    return pattern;
    };

    var setupTimingPattern = function() {

    for (var r = 8; r < _moduleCount - 8; r += 1) {
        if (_modules[r][6] != null) {
        continue;
        }
        _modules[r][6] = (r % 2 == 0);
    }

    for (var c = 8; c < _moduleCount - 8; c += 1) {
        if (_modules[6][c] != null) {
        continue;
        }
        _modules[6][c] = (c % 2 == 0);
    }
    };

    var setupPositionAdjustPattern = function() {

    var pos = QRUtil.getPatternPosition(_typeNumber);

    for (var i = 0; i < pos.length; i += 1) {

        for (var j = 0; j < pos.length; j += 1) {

        var row = pos[i];
        var col = pos[j];

        if (_modules[row][col] != null) {
            continue;
        }

        for (var r = -2; r <= 2; r += 1) {

            for (var c = -2; c <= 2; c += 1) {

            if (r == -2 || r == 2 || c == -2 || c == 2
                || (r == 0 && c == 0) ) {
                _modules[row + r][col + c] = true;
            } else {
                _modules[row + r][col + c] = false;
            }
            }
        }
        }
    }
    };

    var setupTypeNumber = function(test) {

    var bits = QRUtil.getBCHTypeNumber(_typeNumber);

    for (var i = 0; i < 18; i += 1) {
        var mod = (!test && ( (bits >> i) & 1) == 1);
        _modules[Math.floor(i / 3)][i % 3 + _moduleCount - 8 - 3] = mod;
    }

    for (var i = 0; i < 18; i += 1) {
        var mod = (!test && ( (bits >> i) & 1) == 1);
        _modules[i % 3 + _moduleCount - 8 - 3][Math.floor(i / 3)] = mod;
    }
    };

    var setupTypeInfo = function(test, maskPattern) {

    var data = (_errorCorrectLevel << 3) | maskPattern;
    var bits = QRUtil.getBCHTypeInfo(data);

    // vertical
    for (var i = 0; i < 15; i += 1) {

        var mod = (!test && ( (bits >> i) & 1) == 1);

        if (i < 6) {
        _modules[i][8] = mod;
        } else if (i < 8) {
        _modules[i + 1][8] = mod;
        } else {
        _modules[_moduleCount - 15 + i][8] = mod;
        }
    }

    // horizontal
    for (var i = 0; i < 15; i += 1) {

        var mod = (!test && ( (bits >> i) & 1) == 1);

        if (i < 8) {
        _modules[8][_moduleCount - i - 1] = mod;
        } else if (i < 9) {
        _modules[8][15 - i - 1 + 1] = mod;
        } else {
        _modules[8][15 - i - 1] = mod;
        }
    }

    // fixed module
    _modules[_moduleCount - 8][8] = (!test);
    };

    var mapData = function(data, maskPattern) {

    var inc = -1;
    var row = _moduleCount - 1;
    var bitIndex = 7;
    var byteIndex = 0;
    var maskFunc = QRUtil.getMaskFunction(maskPattern);

    for (var col = _moduleCount - 1; col > 0; col -= 2) {

        if (col == 6) col -= 1;

        while (true) {

        for (var c = 0; c < 2; c += 1) {

            if (_modules[row][col - c] == null) {

            var dark = false;

            if (byteIndex < data.length) {
                dark = ( ( (data[byteIndex] >>> bitIndex) & 1) == 1);
            }

            var mask = maskFunc(row, col - c);

            if (mask) {
                dark = !dark;
            }

            _modules[row][col - c] = dark;
            bitIndex -= 1;

            if (bitIndex == -1) {
                byteIndex += 1;
                bitIndex = 7;
            }
            }
        }

        row += inc;

        if (row < 0 || _moduleCount <= row) {
            row -= inc;
            inc = -inc;
            break;
        }
        }
    }
    };

    var createBytes = function(buffer, rsBlocks) {

    var offset = 0;

    var maxDcCount = 0;
    var maxEcCount = 0;

    var dcdata = new Array(rsBlocks.length);
    var ecdata = new Array(rsBlocks.length);

    for (var r = 0; r < rsBlocks.length; r += 1) {

        var dcCount = rsBlocks[r].dataCount;
        var ecCount = rsBlocks[r].totalCount - dcCount;

        maxDcCount = Math.max(maxDcCount, dcCount);
        maxEcCount = Math.max(maxEcCount, ecCount);

        dcdata[r] = new Array(dcCount);

        for (var i = 0; i < dcdata[r].length; i += 1) {
        dcdata[r][i] = 0xff & buffer.getBuffer()[i + offset];
        }
        offset += dcCount;

        var rsPoly = QRUtil.getErrorCorrectPolynomial(ecCount);
        var rawPoly = qrPolynomial(dcdata[r], rsPoly.getLength() - 1);

        var modPoly = rawPoly.mod(rsPoly);
        ecdata[r] = new Array(rsPoly.getLength() - 1);
        for (var i = 0; i < ecdata[r].length; i += 1) {
        var modIndex = i + modPoly.getLength() - ecdata[r].length;
        ecdata[r][i] = (modIndex >= 0)? modPoly.getAt(modIndex) : 0;
        }
    }

    var totalCodeCount = 0;
    for (var i = 0; i < rsBlocks.length; i += 1) {
        totalCodeCount += rsBlocks[i].totalCount;
    }

    var data = new Array(totalCodeCount);
    var index = 0;

    for (var i = 0; i < maxDcCount; i += 1) {
        for (var r = 0; r < rsBlocks.length; r += 1) {
        if (i < dcdata[r].length) {
            data[index] = dcdata[r][i];
            index += 1;
        }
        }
    }

    for (var i = 0; i < maxEcCount; i += 1) {
        for (var r = 0; r < rsBlocks.length; r += 1) {
        if (i < ecdata[r].length) {
            data[index] = ecdata[r][i];
            index += 1;
        }
        }
    }

    return data;
    };

    var createData = function(typeNumber, errorCorrectLevel, dataList) {

    var rsBlocks = QRRSBlock.getRSBlocks(typeNumber, errorCorrectLevel);

    var buffer = qrBitBuffer();

    for (var i = 0; i < dataList.length; i += 1) {
        var data = dataList[i];
        buffer.put(data.getMode(), 4);
        buffer.put(data.getLength(), QRUtil.getLengthInBits(data.getMode(), typeNumber) );
        data.write(buffer);
    }

    // calc num max data.
    var totalDataCount = 0;
    for (var i = 0; i < rsBlocks.length; i += 1) {
        totalDataCount += rsBlocks[i].dataCount;
    }

    if (buffer.getLengthInBits() > totalDataCount * 8) {
        throw new Error('code length overflow. ('
                + buffer.getLengthInBits()
                + '>'
                + totalDataCount * 8
                + ')');
    }

    // end code
    if (buffer.getLengthInBits() + 4 <= totalDataCount * 8) {
        buffer.put(0, 4);
    }

    // padding
    while (buffer.getLengthInBits() % 8 != 0) {
        buffer.putBit(false);
    }

    // padding
    while (true) {

        if (buffer.getLengthInBits() >= totalDataCount * 8) {
        break;
        }
        buffer.put(PAD0, 8);

        if (buffer.getLengthInBits() >= totalDataCount * 8) {
        break;
        }
        buffer.put(PAD1, 8);
    }

    return createBytes(buffer, rsBlocks);
    };

    _this.addData = function(data) {
    var newData = qr8BitByte(data);
    _dataList.push(newData);
    _dataCache = null;
    };

    _this.isDark = function(row, col) {
    if (row < 0 || _moduleCount <= row || col < 0 || _moduleCount <= col) {
        throw new Error(row + ',' + col);
    }
    return _modules[row][col];
    };

    _this.getModuleCount = function() {
    return _moduleCount;
    };

    _this.make = function() {
    makeImpl(false, getBestMaskPattern() );
    };

    _this.createTableTag = function(cellSize, margin) {

    cellSize = cellSize || 2;
    margin = (typeof margin == 'undefined')? cellSize * 4 : margin;

    var qrHtml = '';

    qrHtml += '<table style="';
    qrHtml += ' border- 0px; border-style: none;';
    qrHtml += ' border-collapse: collapse;';
    qrHtml += ' padding: 0px; margin: ' + margin + 'px;';
    qrHtml += '">';
    qrHtml += '<tbody>';

    for (var r = 0; r < _this.getModuleCount(); r += 1) {

        qrHtml += '<tr>';

        for (var c = 0; c < _this.getModuleCount(); c += 1) {
        qrHtml += '<td style="';
        qrHtml += ' border- 0px; border-style: none;';
        qrHtml += ' border-collapse: collapse;';
        qrHtml += ' padding: 0px; margin: 0px;';
        qrHtml += '  ' + cellSize + 'px;';
        qrHtml += ' height: ' + cellSize + 'px;';
        qrHtml += ' background-color: ';
        qrHtml += _this.isDark(r, c)? '#000000' : '#ffffff';
        qrHtml += ';';
        qrHtml += '"/>';
        }

        qrHtml += '</tr>';
    }

    qrHtml += '</tbody>';
    qrHtml += '</table>';

    return qrHtml;
    };

    _this.createImgTag = function(cellSize, margin, size) {

    cellSize = cellSize || 2;
    margin = (typeof margin == 'undefined')? cellSize * 4 : margin;

    var min = margin;
    var max = _this.getModuleCount() * cellSize + margin;

    return createImgTag(size, size, function(x, y) {
        if (min <= x && x < max && min <= y && y < max) {
        var c = Math.floor( (x - min) / cellSize);
        var r = Math.floor( (y - min) / cellSize);
        return _this.isDark(r, c)? 0 : 1;
        } else {
        return 1;
        }
    } );
    };

    return _this;
};

//---------------------------------------------------------------------
// qrcode.stringToBytes
//---------------------------------------------------------------------

qrcode.stringToBytes = function(s) {
    var bytes = new Array();
    for (var i = 0; i < s.length; i += 1) {
    var c = s.charCodeAt(i);
    bytes.push(c & 0xff);
    }
    return bytes;
};

//---------------------------------------------------------------------
// qrcode.createStringToBytes
//---------------------------------------------------------------------

/**
 * @param unicodeData base64 string of byte array.
 * [16bit Unicode],[16bit Bytes], ...
 * @param numChars
 */
qrcode.createStringToBytes = function(unicodeData, numChars) {

    // create conversion map.

    var unicodeMap = function() {

    var bin = base64DecodeInputStream(unicodeData);
    var read = function() {
        var b = bin.read();
        if (b == -1) throw new Error();
        return b;
    };

    var count = 0;
    var unicodeMap = {};
    while (true) {
        var b0 = bin.read();
        if (b0 == -1) break;
        var b1 = read();
        var b2 = read();
        var b3 = read();
        var k = String.fromCharCode( (b0 << 8) | b1);
        var v = (b2 << 8) | b3;
        unicodeMap[k] = v;
        count += 1;
    }
    if (count != numChars) {
        throw new Error(count + ' != ' + numChars);
    }

    return unicodeMap;
    }();

    var unknownChar = '?'.charCodeAt(0);

    return function(s) {
    var bytes = new Array();
    for (var i = 0; i < s.length; i += 1) {
        var c = s.charCodeAt(i);
        if (c < 128) {
        bytes.push(c);
        } else {
        var b = unicodeMap[s.charAt(i)];
        if (typeof b == 'number') {
            if ( (b & 0xff) == b) {
            // 1byte
            bytes.push(b);
            } else {
            // 2bytes
            bytes.push(b >>> 8);
            bytes.push(b & 0xff);
            }
        } else {
            bytes.push(unknownChar);
        }
        }
    }
    return bytes;
    };
};

//---------------------------------------------------------------------
// QRMode
//---------------------------------------------------------------------

var QRMode = {
    MODE_NUMBER :        1 << 0,
    MODE_ALPHA_NUM :     1 << 1,
    MODE_8BIT_BYTE :     1 << 2,
    MODE_KANJI :        1 << 3
};

//---------------------------------------------------------------------
// QRErrorCorrectLevel
//---------------------------------------------------------------------

var QRErrorCorrectLevel = {
    L : 1,
    M : 0,
    Q : 3,
    H : 2
};

//---------------------------------------------------------------------
// QRMaskPattern
//---------------------------------------------------------------------

var QRMaskPattern = {
    PATTERN000 : 0,
    PATTERN001 : 1,
    PATTERN010 : 2,
    PATTERN011 : 3,
    PATTERN100 : 4,
    PATTERN101 : 5,
    PATTERN110 : 6,
    PATTERN111 : 7
};

//---------------------------------------------------------------------
// QRUtil
//---------------------------------------------------------------------

var QRUtil = function() {

    var PATTERN_POSITION_TABLE = [
    [],
    [6, 18],
    [6, 22],
    [6, 26],
    [6, 30],
    [6, 34],
    [6, 22, 38],
    [6, 24, 42],
    [6, 26, 46],
    [6, 28, 50],
    [6, 30, 54],
    [6, 32, 58],
    [6, 34, 62],
    [6, 26, 46, 66],
    [6, 26, 48, 70],
    [6, 26, 50, 74],
    [6, 30, 54, 78],
    [6, 30, 56, 82],
    [6, 30, 58, 86],
    [6, 34, 62, 90],
    [6, 28, 50, 72, 94],
    [6, 26, 50, 74, 98],
    [6, 30, 54, 78, 102],
    [6, 28, 54, 80, 106],
    [6, 32, 58, 84, 110],
    [6, 30, 58, 86, 114],
    [6, 34, 62, 90, 118],
    [6, 26, 50, 74, 98, 122],
    [6, 30, 54, 78, 102, 126],
    [6, 26, 52, 78, 104, 130],
    [6, 30, 56, 82, 108, 134],
    [6, 34, 60, 86, 112, 138],
    [6, 30, 58, 86, 114, 142],
    [6, 34, 62, 90, 118, 146],
    [6, 30, 54, 78, 102, 126, 150],
    [6, 24, 50, 76, 102, 128, 154],
    [6, 28, 54, 80, 106, 132, 158],
    [6, 32, 58, 84, 110, 136, 162],
    [6, 26, 54, 82, 110, 138, 166],
    [6, 30, 58, 86, 114, 142, 170]
    ];
    var G15 = (1 << 10) | (1 << 8) | (1 << 5) | (1 << 4) | (1 << 2) | (1 << 1) | (1 << 0);
    var G18 = (1 << 12) | (1 << 11) | (1 << 10) | (1 << 9) | (1 << 8) | (1 << 5) | (1 << 2) | (1 << 0);
    var G15_MASK = (1 << 14) | (1 << 12) | (1 << 10) | (1 << 4) | (1 << 1);

    var _this = {};

    var getBCHDigit = function(data) {
    var digit = 0;
    while (data != 0) {
        digit += 1;
        data >>>= 1;
    }
    return digit;
    };

    _this.getBCHTypeInfo = function(data) {
    var d = data << 10;
    while (getBCHDigit(d) - getBCHDigit(G15) >= 0) {
        d ^= (G15 << (getBCHDigit(d) - getBCHDigit(G15) ) );
    }
    return ( (data << 10) | d) ^ G15_MASK;
    };

    _this.getBCHTypeNumber = function(data) {
    var d = data << 12;
    while (getBCHDigit(d) - getBCHDigit(G18) >= 0) {
        d ^= (G18 << (getBCHDigit(d) - getBCHDigit(G18) ) );
    }
    return (data << 12) | d;
    };

    _this.getPatternPosition = function(typeNumber) {
    return PATTERN_POSITION_TABLE[typeNumber - 1];
    };

    _this.getMaskFunction = function(maskPattern) {

    switch (maskPattern) {

        case QRMaskPattern.PATTERN000 :
        return function(i, j) { return (i + j) % 2 == 0; };
        case QRMaskPattern.PATTERN001 :
        return function(i, j) { return i % 2 == 0; };
        case QRMaskPattern.PATTERN010 :
        return function(i, j) { return j % 3 == 0; };
        case QRMaskPattern.PATTERN011 :
        return function(i, j) { return (i + j) % 3 == 0; };
        case QRMaskPattern.PATTERN100 :
        return function(i, j) { return (Math.floor(i / 2) + Math.floor(j / 3) ) % 2 == 0; };
        case QRMaskPattern.PATTERN101 :
        return function(i, j) { return (i * j) % 2 + (i * j) % 3 == 0; };
        case QRMaskPattern.PATTERN110 :
        return function(i, j) { return ( (i * j) % 2 + (i * j) % 3) % 2 == 0; };
        case QRMaskPattern.PATTERN111 :
        return function(i, j) { return ( (i * j) % 3 + (i + j) % 2) % 2 == 0; };

        default :
        throw new Error('bad maskPattern:' + maskPattern);
    }
    };

    _this.getErrorCorrectPolynomial = function(errorCorrectLength) {
    var a = qrPolynomial([1], 0);
    for (var i = 0; i < errorCorrectLength; i += 1) {
        a = a.multiply(qrPolynomial([1, QRMath.gexp(i)], 0) );
    }
    return a;
    };

    _this.getLengthInBits = function(mode, type) {

    if (1 <= type && type < 10) {

        // 1 - 9

        switch(mode) {
        case QRMode.MODE_NUMBER     : return 10;
        case QRMode.MODE_ALPHA_NUM     : return 9;
        case QRMode.MODE_8BIT_BYTE    : return 8;
        case QRMode.MODE_KANJI        : return 8;
            default :
            throw new Error('mode:' + mode);
        }

    } else if (type < 27) {

        // 10 - 26

        switch(mode) {
        case QRMode.MODE_NUMBER     : return 12;
        case QRMode.MODE_ALPHA_NUM     : return 11;
        case QRMode.MODE_8BIT_BYTE    : return 16;
        case QRMode.MODE_KANJI        : return 10;
            default :
            throw new Error('mode:' + mode);
        }

    } else if (type < 41) {

        // 27 - 40

        switch(mode) {
        case QRMode.MODE_NUMBER     : return 14;
        case QRMode.MODE_ALPHA_NUM    : return 13;
        case QRMode.MODE_8BIT_BYTE    : return 16;
        case QRMode.MODE_KANJI        : return 12;
            default :
            throw new Error('mode:' + mode);
        }

    } else {
        throw new Error('type:' + type);
    }
    };

    _this.getLostPoint = function(qrcode) {

    var moduleCount = qrcode.getModuleCount();

    var lostPoint = 0;

    // LEVEL1

    for (var row = 0; row < moduleCount; row += 1) {
        for (var col = 0; col < moduleCount; col += 1) {

        var sameCount = 0;
        var dark = qrcode.isDark(row, col);

        for (var r = -1; r <= 1; r += 1) {

            if (row + r < 0 || moduleCount <= row + r) {
            continue;
            }

            for (var c = -1; c <= 1; c += 1) {

            if (col + c < 0 || moduleCount <= col + c) {
                continue;
            }

            if (r == 0 && c == 0) {
                continue;
            }

            if (dark == qrcode.isDark(row + r, col + c) ) {
                sameCount += 1;
            }
            }
        }

        if (sameCount > 5) {
            lostPoint += (3 + sameCount - 5);
        }
        }
    };

    // LEVEL2

    for (var row = 0; row < moduleCount - 1; row += 1) {
        for (var col = 0; col < moduleCount - 1; col += 1) {
        var count = 0;
        if (qrcode.isDark(row, col) ) count += 1;
        if (qrcode.isDark(row + 1, col) ) count += 1;
        if (qrcode.isDark(row, col + 1) ) count += 1;
        if (qrcode.isDark(row + 1, col + 1) ) count += 1;
        if (count == 0 || count == 4) {
            lostPoint += 3;
        }
        }
    }

    // LEVEL3

    for (var row = 0; row < moduleCount; row += 1) {
        for (var col = 0; col < moduleCount - 6; col += 1) {
        if (qrcode.isDark(row, col)
            && !qrcode.isDark(row, col + 1)
            &&  qrcode.isDark(row, col + 2)
            &&  qrcode.isDark(row, col + 3)
            &&  qrcode.isDark(row, col + 4)
            && !qrcode.isDark(row, col + 5)
            &&  qrcode.isDark(row, col + 6) ) {
            lostPoint += 40;
        }
        }
    }

    for (var col = 0; col < moduleCount; col += 1) {
        for (var row = 0; row < moduleCount - 6; row += 1) {
        if (qrcode.isDark(row, col)
            && !qrcode.isDark(row + 1, col)
            &&  qrcode.isDark(row + 2, col)
            &&  qrcode.isDark(row + 3, col)
            &&  qrcode.isDark(row + 4, col)
            && !qrcode.isDark(row + 5, col)
            &&  qrcode.isDark(row + 6, col) ) {
            lostPoint += 40;
        }
        }
    }

    // LEVEL4

    var darkCount = 0;

    for (var col = 0; col < moduleCount; col += 1) {
        for (var row = 0; row < moduleCount; row += 1) {
        if (qrcode.isDark(row, col) ) {
            darkCount += 1;
        }
        }
    }

    var ratio = Math.abs(100 * darkCount / moduleCount / moduleCount - 50) / 5;
    lostPoint += ratio * 10;

    return lostPoint;
    };

    return _this;
}();

//---------------------------------------------------------------------
// QRMath
//---------------------------------------------------------------------

var QRMath = function() {

    var EXP_TABLE = new Array(256);
    var LOG_TABLE = new Array(256);

    // initialize tables
    for (var i = 0; i < 8; i += 1) {
    EXP_TABLE[i] = 1 << i;
    }
    for (var i = 8; i < 256; i += 1) {
    EXP_TABLE[i] = EXP_TABLE[i - 4]
        ^ EXP_TABLE[i - 5]
        ^ EXP_TABLE[i - 6]
        ^ EXP_TABLE[i - 8];
    }
    for (var i = 0; i < 255; i += 1) {
    LOG_TABLE[EXP_TABLE[i] ] = i;
    }

    var _this = {};

    _this.glog = function(n) {

    if (n < 1) {
        throw new Error('glog(' + n + ')');
    }

    return LOG_TABLE[n];
    };

    _this.gexp = function(n) {

    while (n < 0) {
        n += 255;
    }

    while (n >= 256) {
        n -= 255;
    }

    return EXP_TABLE[n];
    };

    return _this;
}();

//---------------------------------------------------------------------
// qrPolynomial
//---------------------------------------------------------------------

function qrPolynomial(num, shift) {

    if (typeof num.length == 'undefined') {
    throw new Error(num.length + '/' + shift);
    }

    var _num = function() {
    var offset = 0;
    while (offset < num.length && num[offset] == 0) {
        offset += 1;
    }
    var _num = new Array(num.length - offset + shift);
    for (var i = 0; i < num.length - offset; i += 1) {
        _num[i] = num[i + offset];
    }
    return _num;
    }();

    var _this = {};

    _this.getAt = function(index) {
    return _num[index];
    };

    _this.getLength = function() {
    return _num.length;
    };

    _this.multiply = function(e) {

    var num = new Array(_this.getLength() + e.getLength() - 1);

    for (var i = 0; i < _this.getLength(); i += 1) {
        for (var j = 0; j < e.getLength(); j += 1) {
        num[i + j] ^= QRMath.gexp(QRMath.glog(_this.getAt(i) ) + QRMath.glog(e.getAt(j) ) );
        }
    }

    return qrPolynomial(num, 0);
    };

    _this.mod = function(e) {

    if (_this.getLength() - e.getLength() < 0) {
        return _this;
    }

    var ratio = QRMath.glog(_this.getAt(0) ) - QRMath.glog(e.getAt(0) );

    var num = new Array(_this.getLength() );
    for (var i = 0; i < _this.getLength(); i += 1) {
        num[i] = _this.getAt(i);
    }

    for (var i = 0; i < e.getLength(); i += 1) {
        num[i] ^= QRMath.gexp(QRMath.glog(e.getAt(i) ) + ratio);
    }

    // recursive call
    return qrPolynomial(num, 0).mod(e);
    };

    return _this;
};

//---------------------------------------------------------------------
// QRRSBlock
//---------------------------------------------------------------------

var QRRSBlock = function() {


    // [1: [L, M, Q, H], ..]
    var RS_BLOCK_TABLE=[[1,26,19],[1,26,16],[1,26,13],[1,26,9],[1,44,34],[1,44,28],[1,44,22],[1,44,16],[1,70,55],[1,70,44],[2,35,17],[2,35,13],[1,100,80],[2,50,32],[2,50,24],[4,25,9],[1,134,108],[2,67,43],[2,33,15,2,34,16],[2,33,11,2,34,12],[2,86,68],[4,43,27],[4,43,19],[4,43,15],[2,98,78],[4,49,31],[2,32,14,4,33,15],[4,39,13,1,40,14],[2,121,97],[2,60,38,2,61,39],[4,40,18,2,41,19],[4,40,14,2,41,15],[2,146,116],[3,58,36,2,59,37],[4,36,16,4,37,17],[4,36,12,4,37,13],[2,86,68,2,87,69],[4,69,43,1,70,44],[6,43,19,2,44,20],[6,43,15,2,44,16],[4,101,81],[1,80,50,4,81,51],[4,50,22,4,51,23],[3,36,12,8,37,13],[2,116,92,2,117,93],[6,58,36,2,59,37],[4,46,20,6,47,21],[7,42,14,4,43,15],[4,133,107],[8,59,37,1,60,38],[8,44,20,4,45,21],[12,33,11,4,34,12],[3,145,115,1,146,116],[4,64,40,5,65,41],[11,36,16,5,37,17],[11,36,12,5,37,13],[5,109,87,1,110,88],[5,65,41,5,66,42],[5,54,24,7,55,25],[11,36,12],[5,122,98,1,123,99],[7,73,45,3,74,46],[15,43,19,2,44,20],[3,45,15,13,46,16],[1,135,107,5,136,108],[10,74,46,1,75,47],[1,50,22,15,51,23],[2,42,14,17,43,15],[5,150,120,1,151,121],[9,69,43,4,70,44],[17,50,22,1,51,23],[2,42,14,19,43,15],[3,141,113,4,142,114],[3,70,44,11,71,45],[17,47,21,4,48,22],[9,39,13,16,40,14],[3,135,107,5,136,108],[3,67,41,13,68,42],[15,54,24,5,55,25],[15,43,15,10,44,16],[4,144,116,4,145,117],[17,68,42],[17,50,22,6,51,23],[19,46,16,6,47,17],[2,139,111,7,140,112],[17,74,46],[7,54,24,16,55,25],[34,37,13],[4,151,121,5,152,122],[4,75,47,14,76,48],[11,54,24,14,55,25],[16,45,15,14,46,16],[6,147,117,4,148,118],[6,73,45,14,74,46],[11,54,24,16,55,25],[30,46,16,2,47,17],[8,132,106,4,133,107],[8,75,47,13,76,48],[7,54,24,22,55,25],[22,45,15,13,46,16],[10,142,114,2,143,115],[19,74,46,4,75,47],[28,50,22,6,51,23],[33,46,16,4,47,17],[8,152,122,4,153,123],[22,73,45,3,74,46],[8,53,23,26,54,24],[12,45,15,28,46,16],[3,147,117,10,148,118],[3,73,45,23,74,46],[4,54,24,31,55,25],[11,45,15,31,46,16],[7,146,116,7,147,117],[21,73,45,7,74,46],[1,53,23,37,54,24],[19,45,15,26,46,16],[5,145,115,10,146,116],[19,75,47,10,76,48],[15,54,24,25,55,25],[23,45,15,25,46,16],[13,145,115,3,146,116],[2,74,46,29,75,47],[42,54,24,1,55,25],[23,45,15,28,46,16],[17,145,115],[10,74,46,23,75,47],[10,54,24,35,55,25],[19,45,15,35,46,16],[17,145,115,1,146,116],[14,74,46,21,75,47],[29,54,24,19,55,25],[11,45,15,46,46,16],[13,145,115,6,146,116],[14,74,46,23,75,47],[44,54,24,7,55,25],[59,46,16,1,47,17],[12,151,121,7,152,122],[12,75,47,26,76,48],[39,54,24,14,55,25],[22,45,15,41,46,16],[6,151,121,14,152,122],[6,75,47,34,76,48],[46,54,24,10,55,25],[2,45,15,64,46,16],[17,152,122,4,153,123],[29,74,46,14,75,47],[49,54,24,10,55,25],[24,45,15,46,46,16],[4,152,122,18,153,123],[13,74,46,32,75,47],[48,54,24,14,55,25],[42,45,15,32,46,16],[20,147,117,4,148,118],[40,75,47,7,76,48],[43,54,24,22,55,25],[10,45,15,67,46,16],[19,148,118,6,149,119],[18,75,47,31,76,48],[34,54,24,34,55,25],[20,45,15,61,46,16]];

    var qrRSBlock = function(totalCount, dataCount) {
    var _this = {};
    _this.totalCount = totalCount;
    _this.dataCount = dataCount;
    return _this;
    };

    var _this = {};

    var getRsBlockTable = function(typeNumber, errorCorrectLevel) {

    switch(errorCorrectLevel) {
        case QRErrorCorrectLevel.L :
        return RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 0];
        case QRErrorCorrectLevel.M :
        return RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 1];
        case QRErrorCorrectLevel.Q :
        return RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 2];
        case QRErrorCorrectLevel.H :
        return RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 3];
        default :
        return undefined;
    }
    };

    _this.getRSBlocks = function(typeNumber, errorCorrectLevel) {

    var rsBlock = getRsBlockTable(typeNumber, errorCorrectLevel);

    if (typeof rsBlock == 'undefined') {
        throw new Error('bad rs block @ typeNumber:' + typeNumber +
                '/errorCorrectLevel:' + errorCorrectLevel);
    }

    var length = rsBlock.length / 3;

    var list = new Array();

    for (var i = 0; i < length; i += 1) {

        var count = rsBlock[i * 3 + 0];
        var totalCount = rsBlock[i * 3 + 1];
        var dataCount = rsBlock[i * 3 + 2];

        for (var j = 0; j < count; j += 1) {
        list.push(qrRSBlock(totalCount, dataCount) );
        }
    }

    return list;
    };

    return _this;
}();

//---------------------------------------------------------------------
// qrBitBuffer
//---------------------------------------------------------------------

var qrBitBuffer = function() {

    var _buffer = new Array();
    var _length = 0;

    var _this = {};

    _this.getBuffer = function() {
    return _buffer;
    };

    _this.getAt = function(index) {
    var bufIndex = Math.floor(index / 8);
    return ( (_buffer[bufIndex] >>> (7 - index % 8) ) & 1) == 1;
    };

    _this.put = function(num, length) {
    for (var i = 0; i < length; i += 1) {
        _this.putBit( ( (num >>> (length - i - 1) ) & 1) == 1);
    }
    };

    _this.getLengthInBits = function() {
    return _length;
    };

    _this.putBit = function(bit) {

    var bufIndex = Math.floor(_length / 8);
    if (_buffer.length <= bufIndex) {
        _buffer.push(0);
    }

    if (bit) {
        _buffer[bufIndex] |= (0x80 >>> (_length % 8) );
    }

    _length += 1;
    };

    return _this;
};

//---------------------------------------------------------------------
// qr8BitByte
//---------------------------------------------------------------------

var qr8BitByte = function(data) {

    var _mode = QRMode.MODE_8BIT_BYTE;
    var _data = data;
    var _parsedData = [];

    var _this = {};


    // Added to support UTF-8 Characters
    for (var i = 0, l = _data.length; i < l; i++) {
    var byteArray = [];
    var code = _data.charCodeAt(i);

    if (code > 0x10000) {
        byteArray[0] = 0xF0 | ((code & 0x1C0000) >>> 18);
        byteArray[1] = 0x80 | ((code & 0x3F000) >>> 12);
        byteArray[2] = 0x80 | ((code & 0xFC0) >>> 6);
        byteArray[3] = 0x80 | (code & 0x3F);
    } else if (code > 0x800) {
        byteArray[0] = 0xE0 | ((code & 0xF000) >>> 12);
        byteArray[1] = 0x80 | ((code & 0xFC0) >>> 6);
        byteArray[2] = 0x80 | (code & 0x3F);
    } else if (code > 0x80) {
        byteArray[0] = 0xC0 | ((code & 0x7C0) >>> 6);
        byteArray[1] = 0x80 | (code & 0x3F);
    } else {
        byteArray[0] = code;
    }

        // Fix Unicode corruption bug
        _parsedData.push(byteArray);
    }

    _parsedData = Array.prototype.concat.apply([], _parsedData);

    if (_parsedData.length != _data.length) {
    _parsedData.unshift(191);
    _parsedData.unshift(187);
    _parsedData.unshift(239);
    }

    var _bytes = _parsedData;

    _this.getMode = function() {
    return _mode;
    };

    _this.getLength = function(buffer) {
    return _bytes.length;
    };

    _this.write = function(buffer) {
    for (var i = 0; i < _bytes.length; i += 1) {
        buffer.put(_bytes[i], 8);
    }
    };

    return _this;
};

//=====================================================================
// GIF Support etc.
//

//---------------------------------------------------------------------
// byteArrayOutputStream
//---------------------------------------------------------------------

var byteArrayOutputStream = function() {

    var _bytes = new Array();

    var _this = {};

    _this.writeByte = function(b) {
    _bytes.push(b & 0xff);
    };

    _this.writeShort = function(i) {
    _this.writeByte(i);
    _this.writeByte(i >>> 8);
    };

    _this.writeBytes = function(b, off, len) {
    off = off || 0;
    len = len || b.length;
    for (var i = 0; i < len; i += 1) {
        _this.writeByte(b[i + off]);
    }
    };

    _this.writeString = function(s) {
    for (var i = 0; i < s.length; i += 1) {
        _this.writeByte(s.charCodeAt(i) );
    }
    };

    _this.toByteArray = function() {
    return _bytes;
    };

    _this.toString = function() {
    var s = '';
    s += '[';
    for (var i = 0; i < _bytes.length; i += 1) {
        if (i > 0) {
        s += ',';
        }
        s += _bytes[i];
    }
    s += ']';
    return s;
    };

    return _this;
};

//---------------------------------------------------------------------
// base64EncodeOutputStream
//---------------------------------------------------------------------

var base64EncodeOutputStream = function() {

    var _buffer = 0;
    var _buflen = 0;
    var _length = 0;
    var _base64 = '';

    var _this = {};

    var writeEncoded = function(b) {
    _base64 += String.fromCharCode(encode(b & 0x3f) );
    };

    var encode = function(n) {
    if (n < 0) {
        // error.
    } else if (n < 26) {
        return 0x41 + n;
    } else if (n < 52) {
        return 0x61 + (n - 26);
    } else if (n < 62) {
        return 0x30 + (n - 52);
    } else if (n == 62) {
        return 0x2b;
    } else if (n == 63) {
        return 0x2f;
    }
    throw new Error('n:' + n);
    };

    _this.writeByte = function(n) {

    _buffer = (_buffer << 8) | (n & 0xff);
    _buflen += 8;
    _length += 1;

    while (_buflen >= 6) {
        writeEncoded(_buffer >>> (_buflen - 6) );
        _buflen -= 6;
    }
    };

    _this.flush = function() {

    if (_buflen > 0) {
        writeEncoded(_buffer << (6 - _buflen) );
        _buffer = 0;
        _buflen = 0;
    }

    if (_length % 3 != 0) {
        // padding
        var padlen = 3 - _length % 3;
        for (var i = 0; i < padlen; i += 1) {
        _base64 += '=';
        }
    }
    };

    _this.toString = function() {
    return _base64;
    };

    return _this;
};

//---------------------------------------------------------------------
// base64DecodeInputStream
//---------------------------------------------------------------------

var base64DecodeInputStream = function(str) {

    var _str = str;
    var _pos = 0;
    var _buffer = 0;
    var _buflen = 0;

    var _this = {};

    _this.read = function() {

    while (_buflen < 8) {

        if (_pos >= _str.length) {
        if (_buflen == 0) {
            return -1;
        }
        throw new Error('unexpected end of file./' + _buflen);
        }

        var c = _str.charAt(_pos);
        _pos += 1;

        if (c == '=') {
        _buflen = 0;
        return -1;
        } else if (c.match(/^s$/) ) {
        // ignore if whitespace.
        continue;
        }

        _buffer = (_buffer << 6) | decode(c.charCodeAt(0) );
        _buflen += 6;
    }

    var n = (_buffer >>> (_buflen - 8) ) & 0xff;
    _buflen -= 8;
    return n;
    };

    var decode = function(c) {
    if (0x41 <= c && c <= 0x5a) {
        return c - 0x41;
    } else if (0x61 <= c && c <= 0x7a) {
        return c - 0x61 + 26;
    } else if (0x30 <= c && c <= 0x39) {
        return c - 0x30 + 52;
    } else if (c == 0x2b) {
        return 62;
    } else if (c == 0x2f) {
        return 63;
    } else {
        throw new Error('c:' + c);
    }
    };

    return _this;
};

//---------------------------------------------------------------------
// gifImage (B/W)
//---------------------------------------------------------------------

var gifImage = function(width, height) {

    var _width = width;
    var _height = height;
    var _data = new Array(width * height);

    var _this = {};

    _this.setPixel = function(x, y, pixel) {
    _data[y * _width + x] = pixel;
    };

    _this.write = function(out) {

    //---------------------------------
    // GIF Signature

    out.writeString('GIF87a');

    //---------------------------------
    // Screen Descriptor

    out.writeShort(_width);
    out.writeShort(_height);

    out.writeByte(0x80); // 2bit
    out.writeByte(0);
    out.writeByte(0);

    //---------------------------------
    // Global Color Map

    // black
    out.writeByte(0x00);
    out.writeByte(0x00);
    out.writeByte(0x00);

    // white
    out.writeByte(0xff);
    out.writeByte(0xff);
    out.writeByte(0xff);

    //---------------------------------
    // Image Descriptor

    out.writeString(',');
    out.writeShort(0);
    out.writeShort(0);
    out.writeShort(_width);
    out.writeShort(_height);
    out.writeByte(0);

    //---------------------------------
    // Local Color Map

    //---------------------------------
    // Raster Data

    var lzwMinCodeSize = 2;
    var raster = getLZWRaster(lzwMinCodeSize);

    out.writeByte(lzwMinCodeSize);

    var offset = 0;

    while (raster.length - offset > 255) {
        out.writeByte(255);
        out.writeBytes(raster, offset, 255);
        offset += 255;
    }

    out.writeByte(raster.length - offset);
    out.writeBytes(raster, offset, raster.length - offset);
    out.writeByte(0x00);

    //---------------------------------
    // GIF Terminator
    out.writeString(';');
    };

    var bitOutputStream = function(out) {

    var _out = out;
    var _bitLength = 0;
    var _bitBuffer = 0;

    var _this = {};

    _this.write = function(data, length) {

        if ( (data >>> length) != 0) {
        throw new Error('length over');
        }

        while (_bitLength + length >= 8) {
        _out.writeByte(0xff & ( (data << _bitLength) | _bitBuffer) );
        length -= (8 - _bitLength);
        data >>>= (8 - _bitLength);
        _bitBuffer = 0;
        _bitLength = 0;
        }

        _bitBuffer = (data << _bitLength) | _bitBuffer;
        _bitLength = _bitLength + length;
    };

    _this.flush = function() {
        if (_bitLength > 0) {
        _out.writeByte(_bitBuffer);
        }
    };

    return _this;
    };

    var getLZWRaster = function(lzwMinCodeSize) {

    var clearCode = 1 << lzwMinCodeSize;
    var endCode = (1 << lzwMinCodeSize) + 1;
    var bitLength = lzwMinCodeSize + 1;

    // Setup LZWTable
    var table = lzwTable();

    for (var i = 0; i < clearCode; i += 1) {
        table.add(String.fromCharCode(i) );
    }
    table.add(String.fromCharCode(clearCode) );
    table.add(String.fromCharCode(endCode) );

    var byteOut = byteArrayOutputStream();
    var bitOut = bitOutputStream(byteOut);

    // clear code
    bitOut.write(clearCode, bitLength);

    var dataIndex = 0;

    var s = String.fromCharCode(_data[dataIndex]);
    dataIndex += 1;

    while (dataIndex < _data.length) {

        var c = String.fromCharCode(_data[dataIndex]);
        dataIndex += 1;

        if (table.contains(s + c) ) {

        s = s + c;

        } else {

        bitOut.write(table.indexOf(s), bitLength);

        if (table.size() < 0xfff) {

            if (table.size() == (1 << bitLength) ) {
            bitLength += 1;
            }

            table.add(s + c);
        }

        s = c;
        }
    }

    bitOut.write(table.indexOf(s), bitLength);

    // end code
    bitOut.write(endCode, bitLength);

    bitOut.flush();

    return byteOut.toByteArray();
    };

    var lzwTable = function() {

    var _map = {};
    var _size = 0;

    var _this = {};

    _this.add = function(key) {
        if (_this.contains(key) ) {
        throw new Error('dup key:' + key);
        }
        _map[key] = _size;
        _size += 1;
    };

    _this.size = function() {
        return _size;
    };

    _this.indexOf = function(key) {
        return _map[key];
    };

    _this.contains = function(key) {
        return typeof _map[key] != 'undefined';
    };

    return _this;
    };

    return _this;
};

var createImgTag = function(width, height, getPixel, alt) {

    var gif = gifImage(width, height);
    for (var y = 0; y < height; y += 1) {
    for (var x = 0; x < width; x += 1) {
        gif.setPixel(x, y, getPixel(x, y) );
    }
    }

    var b = byteArrayOutputStream();
    gif.write(b);

    var base64 = base64EncodeOutputStream();
    var bytes = b.toByteArray();
    for (var i = 0; i < bytes.length; i += 1) {
    base64.writeByte(bytes[i]);
    }
    base64.flush();

    var img = '';
    img += 'data:image/gif;base64,';
    img += base64;

    return img;
};

//---------------------------------------------------------------------
// returns qrcode function.

var drawImg = function(text, options) {
    options = options || {};
    var typeNumber = options.typeNumber || 4;
    var errorCorrectLevel = options.errorCorrectLevel || 'M';
    var size = options.size || 500;

    var qr;

    try {
        qr = qrcode(typeNumber, errorCorrectLevel || 'M');
        qr.addData(text);
        qr.make();
    } catch (e) {
        if(typeNumber >= 40) {
            throw new Error('Text too long to encode');
        } else {
            return drawImg(text, {
                size: size,
                errorCorrectLevel: errorCorrectLevel,
                typeNumber: typeNumber + 1
            });
        }
    }

    // calc cellsize and margin
    var cellsize = parseInt(size / qr.getModuleCount());
    var margin = parseInt((size - qr.getModuleCount() * cellsize) / 2);

    return qr.createImgTag(cellsize, margin, size);
};
module.exports = {
    drawImg: drawImg
};

来自github地址:https://github.com/Pudon/weapp-qrcode-base64