vue后台_纯前端实现excel导出/csv导出

之前的文件下载功能一般是由前后端配合实现，由于项目需要，纯前端实现了一把excel的导出功能：

一、excel导出

1.安装依赖库

xlsx：这是一个功能强大的excel处理库，但是上手难度也很大，还涉及不少二进制的东西

file-saver:ES5新增了相关file,blob,fileList等API，但不是所有浏览器都支持，file-saver在没有原生支持saveAs的浏览器上实现了saveAs()接口

script-loader: 在全局上下文环境中执行一次js脚本。

npm install -D xlsx ,file-saver
npm install -s script-loader

二、引入相关依赖

上述部分依赖不支持import引入，所以需要使用'script-loader'将他们挂载到全局环境下；

其中的blob.js是github上的一个开源文件，对于浏览器不能原生支持blob的情况，提供了兼容解决方案,其地址是：https://github.com/eligrey/Blob.js

require('script-loader!file-saver'); //保存文件用
require('script-loader!vendor/Blob'); //转二进制用
require('script-loader!xlsx/dist/xlsx.core.min'); //xlsx核心

/* eslint-disable */
/* Blob.js
 * A Blob implementation.
 * 2014-05-27
 *
 * By Eli Grey, http://eligrey.com
 * By Devin Samarin, https://github.com/eboyjr
 * License: X11/MIT
 *   See LICENSE.md
 */

/*global self, unescape */
/*jslint bitwise: true, regexp: true, confusion: true, es5: true, vars: true, white: true,
 plusplus: true */

/*! @source http://purl.eligrey.com/github/Blob.js/blob/master/Blob.js */

(function (view) {
    "use strict";

    view.URL = view.URL || view.webkitURL;

    if (view.Blob && view.URL) {
        try {
            new Blob;
            return;
        } catch (e) {}
    }

    // Internally we use a BlobBuilder implementation to base Blob off of
    // in order to support older browsers that only have BlobBuilder
    var BlobBuilder = view.BlobBuilder || view.WebKitBlobBuilder || view.MozBlobBuilder || (function(view) {
            var
                get_class = function(object) {
                    return Object.prototype.toString.call(object).match(/^[objects(.*)]$/)[1];
                }
                , FakeBlobBuilder = function BlobBuilder() {
                    this.data = [];
                }
                , FakeBlob = function Blob(data, type, encoding) {
                    this.data = data;
                    this.size = data.length;
                    this.type = type;
                    this.encoding = encoding;
                }
                , FBB_proto = FakeBlobBuilder.prototype
                , FB_proto = FakeBlob.prototype
                , FileReaderSync = view.FileReaderSync
                , FileException = function(type) {
                    this.code = this[this.name = type];
                }
                , file_ex_codes = (
                    "NOT_FOUND_ERR SECURITY_ERR ABORT_ERR NOT_READABLE_ERR ENCODING_ERR "
                    + "NO_MODIFICATION_ALLOWED_ERR INVALID_STATE_ERR SYNTAX_ERR"
                ).split(" ")
                , file_ex_code = file_ex_codes.length
                , real_URL = view.URL || view.webkitURL || view
                , real_create_object_URL = real_URL.createObjectURL
                , real_revoke_object_URL = real_URL.revokeObjectURL
                , URL = real_URL
                , btoa = view.btoa
                , atob = view.atob

                , ArrayBuffer = view.ArrayBuffer
                , Uint8Array = view.Uint8Array
                ;
            FakeBlob.fake = FB_proto.fake = true;
            while (file_ex_code--) {
                FileException.prototype[file_ex_codes[file_ex_code]] = file_ex_code + 1;
            }
            if (!real_URL.createObjectURL) {
                URL = view.URL = {};
            }
            URL.createObjectURL = function(blob) {
                var
                    type = blob.type
                    , data_URI_header
                    ;
                if (type === null) {
                    type = "application/octet-stream";
                }
                if (blob instanceof FakeBlob) {
                    data_URI_header = "data:" + type;
                    if (blob.encoding === "base64") {
                        return data_URI_header + ";base64," + blob.data;
                    } else if (blob.encoding === "URI") {
                        return data_URI_header + "," + decodeURIComponent(blob.data);
                    } if (btoa) {
                        return data_URI_header + ";base64," + btoa(blob.data);
                    } else {
                        return data_URI_header + "," + encodeURIComponent(blob.data);
                    }
                } else if (real_create_object_URL) {
                    return real_create_object_URL.call(real_URL, blob);
                }
            };
            URL.revokeObjectURL = function(object_URL) {
                if (object_URL.substring(0, 5) !== "data:" && real_revoke_object_URL) {
                    real_revoke_object_URL.call(real_URL, object_URL);
                }
            };
            FBB_proto.append = function(data/*, endings*/) {
                var bb = this.data;
                // decode data to a binary string
                if (Uint8Array && (data instanceof ArrayBuffer || data instanceof Uint8Array)) {
                    var
                        str = ""
                        , buf = new Uint8Array(data)
                        , i = 0
                        , buf_len = buf.length
                        ;
                    for (; i < buf_len; i++) {
                        str += String.fromCharCode(buf[i]);
                    }
                    bb.push(str);
                } else if (get_class(data) === "Blob" || get_class(data) === "File") {
                    if (FileReaderSync) {
                        var fr = new FileReaderSync;
                        bb.push(fr.readAsBinaryString(data));
                    } else {
                        // async FileReader won't work as BlobBuilder is sync
                        throw new FileException("NOT_READABLE_ERR");
                    }
                } else if (data instanceof FakeBlob) {
                    if (data.encoding === "base64" && atob) {
                        bb.push(atob(data.data));
                    } else if (data.encoding === "URI") {
                        bb.push(decodeURIComponent(data.data));
                    } else if (data.encoding === "raw") {
                        bb.push(data.data);
                    }
                } else {
                    if (typeof data !== "string") {
                        data += ""; // convert unsupported types to strings
                    }
                    // decode UTF-16 to binary string
                    bb.push(unescape(encodeURIComponent(data)));
                }
            };
            FBB_proto.getBlob = function(type) {
                if (!arguments.length) {
                    type = null;
                }
                return new FakeBlob(this.data.join(""), type, "raw");
            };
            FBB_proto.toString = function() {
                return "[object BlobBuilder]";
            };
            FB_proto.slice = function(start, end, type) {
                var args = arguments.length;
                if (args < 3) {
                    type = null;
                }
                return new FakeBlob(
                    this.data.slice(start, args > 1 ? end : this.data.length)
                    , type
                    , this.encoding
                );
            };
            FB_proto.toString = function() {
                return "[object Blob]";
            };
            FB_proto.close = function() {
                this.size = this.data.length = 0;
            };
            return FakeBlobBuilder;
        }(view));

    view.Blob = function Blob(blobParts, options) {
        var type = options ? (options.type || "") : "";
        var builder = new BlobBuilder();
        if (blobParts) {
            for (var i = 0, len = blobParts.length; i < len; i++) {
                builder.append(blobParts[i]);
            }
        }
        return builder.getBlob(type);
    };
}(typeof self !== "undefined" && self || typeof window !== "undefined" && window || this.content || this));

三、封装Export2Excel.js，它对外暴露两个接口：export_table_to_excel和export_json_to_excel

/* eslint-disable */
require('script-loader!file-saver');
require('script-loader!./Blob.js');
require('script-loader!xlsx/dist/xlsx.core.min');

function generateArray(table) {
  var out = [];
  var rows = table.querySelectorAll('tr');
  var ranges = [];
  for (var R = 0; R < rows.length; ++R) {
    var outRow = [];
    var row = rows[R];
    var columns = row.querySelectorAll('td');
    for (var C = 0; C < columns.length; ++C) {
      var cell = columns[C];
      var colspan = cell.getAttribute('colspan');
      var rowspan = cell.getAttribute('rowspan');
      var cellValue = cell.innerText;
      if (cellValue !== "" && cellValue == +cellValue) cellValue = +cellValue;

      //Skip ranges
      ranges.forEach(function(range) {
        if (R >= range.s.r && R <= range.e.r && outRow.length >= range.s.c && outRow.length <= range.e.c) {
          for (var i = 0; i <= range.e.c - range.s.c; ++i) outRow.push(null);
        }
      });

      //Handle Row Span
      if (rowspan || colspan) {
        rowspan = rowspan || 1;
        colspan = colspan || 1;
        ranges.push({
          s: {
            r: R,
            c: outRow.length
          },
          e: {
            r: R + rowspan - 1,
            c: outRow.length + colspan - 1
          }
        });
      };

      //Handle Value
      outRow.push(cellValue !== "" ? cellValue : null);

      //Handle Colspan
      if (colspan)
        for (var k = 0; k < colspan - 1; ++k) outRow.push(null);
    }
    out.push(outRow);
  }
  return [out, ranges];
};

function datenum(v, date1904) {
  if (date1904) v += 1462;
  var epoch = Date.parse(v);
  return (epoch - new Date(Date.UTC(1899, 11, 30))) / (24 * 60 * 60 * 1000);
}

function sheet_from_array_of_arrays(data, opts) {
  var ws = {};
  var range = {
    s: {
      c: 10000000,
      r: 10000000
    },
    e: {
      c: 0,
      r: 0
    }
  };
  for (var R = 0; R != data.length; ++R) {
    for (var C = 0; C != data[R].length; ++C) {
      if (range.s.r > R) range.s.r = R;
      if (range.s.c > C) range.s.c = C;
      if (range.e.r < R) range.e.r = R;
      if (range.e.c < C) range.e.c = C;
      var cell = {
        v: data[R][C]
      };
      if (cell.v == null) continue;
      var cell_ref = XLSX.utils.encode_cell({
        c: C,
        r: R
      });

      if (typeof cell.v === 'number') cell.t = 'n';
      else if (typeof cell.v === 'boolean') cell.t = 'b';
      else if (cell.v instanceof Date) {
        cell.t = 'n';
        cell.z = XLSX.SSF._table[14];
        cell.v = datenum(cell.v);
      } else cell.t = 's';

      ws[cell_ref] = cell;
    }
  }
  if (range.s.c < 10000000) ws['!ref'] = XLSX.utils.encode_range(range);
  return ws;
}

function Workbook() {
  if (!(this instanceof Workbook)) return new Workbook();
  this.SheetNames = [];
  this.Sheets = {};
}

function s2ab(s) {
  var buf = new ArrayBuffer(s.length);
  var view = new Uint8Array(buf);
  for (var i = 0; i != s.length; ++i) view[i] = s.charCodeAt(i) & 0xFF;
  return buf;
}

export function export_table_to_excel(id) {
  var theTable = document.getElementById(id);
  console.log('a')
  var oo = generateArray(theTable);
  var ranges = oo[1];

  /* original data */
  var data = oo[0];
  var ws_name = "SheetJS";
  console.log(data);

  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);

  /* add ranges to worksheet */
  // ws['!cols'] = ['apple', 'banan'];
  ws['!merges'] = ranges;

  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: 'xlsx',
    bookSST: false,
    type: 'binary'
  });

  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), "test.xlsx")
}

function formatJson(jsonData) {
  console.log(jsonData)
}
export function export_json_to_excel(th, jsonData, defaultTitle) {

  /* original data */

  var data = jsonData;
  data.unshift(th);
  var ws_name = "SheetJS";

  var wb = new Workbook(),
    ws = sheet_from_array_of_arrays(data);


  /* add worksheet to workbook */
  wb.SheetNames.push(ws_name);
  wb.Sheets[ws_name] = ws;

  var wbout = XLSX.write(wb, {
    bookType: 'xlsx',
    bookSST: false,
    type: 'binary'
  });
  var title = defaultTitle || '列表'
  saveAs(new Blob([s2ab(wbout)], {
    type: "application/octet-stream"
  }), title + ".xlsx")
}

四、调用

handleDownload() {
  require.ensure([], () => { // 用 webpack Code Splitting xlsl还是很大的
    const { export_json_to_excel } = require('vendor/Export2Excel');
    const tHeader = ['序号', '文章标题', '作者', '阅读数', '发布时间']; // excel 表格头
    const filterVal = ['id', 'title', 'author', 'pageviews', 'display_time'];
    const list = this.list;
    const data = this.formatJson(filterVal, list); // 自行洗数据 按序排序的一个array数组
    export_json_to_excel(tHeader, data, '列表excel');
  })
}，
formatJson(filterVal, jsonData) {
  return jsonData.map(v => filterVal.map(j => v[j]))
}

二、csv导出

说实话，如果系统不强制要求excel格式的话，使用csv导出方便太多了,创建一个a标签，写上data:text/csv;charset=utf-8,把数据塞进去，encodeURI(csvContent)就可以了，可以参见自己封装的这个downloadBtn组件

<template>
  <a ref="link" class="download-btn" v-on:click="handleClick">导出</a>
</template>
<script type="text/javascript">
export default {
  props: {
    header: {
      type: Array,
      default: function() {
        return [];
      }
    },
    data: {
      type: Array,
      default: function() {
        return [];
      }
    },
    fileName: {
      type: String,
      default: 'data.csv'
    }
  },
  methods: {
    handleClick: function() {
      if (!this.data || this.data.length <= 0) {
        this.$message({
          message: '请先进行查询,并等待查询结果返回!',
          type: 'error'
        });
        return;
      }
      var csvContent = 'data:text/csv;charset=utf-8,ufeff';
      csvContent += this.headerLabel + '
';
      this.data.forEach((item, index) => {
        let dataString = '';
        for (let i = 0; i < this.headerProp.length; i++) {
          dataString += item[this.headerProp[i]] + ',';
        }
        csvContent += index < this.data.length ? dataString.replace(/,$/, '
') : dataString.replace(/,$/, '');
      });
      this.$refs.link.setAttribute('href', encodeURI(csvContent));
      this.$refs.link.setAttribute('download', this.fileName);
    }
  },
  computed: {
    // 要求head是数组，数组中的每个元素是对象，并且每个对象都有label属性
    headerLabel: function() {
      let result;
      result = this.header.map((item) => {
        return item.label;
      })
      result = result.join(',');
      return result;
    },
    headerProp: function() {
      let result;
      result = this.header.map((item) => {
        return item.prop;
      })
      return result;
    }
  }
}

</script>
<style lang="scss" scoped>
.download-btn {
  display: inline-block;
  margin-left: 10px;
  padding: 2px 15px;
  font-size: 12px;
  border-radius: 4px;
  color: #FFF;
  background-color: #f7ba2a;
  border-color: #f7ba2a;
  outline: 0;
  text-align: center;
  -webkit-appearence: none;
  appearence: none;
  cursor: pointer;
}

</style>