文件下载

JS代码：
var eleTextarea = document.querySelector('textarea');
var eleButton = document.querySelector('input[type="button"]');

// 下载文件方法
var funDownload = function (content, filename) {
    var eleLink = document.createElement('a');
    eleLink.download = filename;
    eleLink.style.display = 'none';
    // 字符内容转变成blob地址
    var blob = new Blob([content]);
    eleLink.href = URL.createObjectURL(blob);
    // 触发点击
    document.body.appendChild(eleLink);
    eleLink.click();
    // 然后移除
    document.body.removeChild(eleLink);
};

if ('download' in document.createElement('a')) {
    // 作为test.html文件下载
    eleButton.addEventListener('click', function () {
        funDownload(eleTextarea.value, 'test.html');    
    });
} else {
    eleButton.onclick = function () {
        alert('浏览器不支持');    
    };
}

三、借助Base64实现任意文件下载

var funDownload = function (domImg, filename) {
    // 创建隐藏的可下载链接
    var eleLink = document.createElement('a');
    eleLink.download = filename;
    eleLink.style.display = 'none';
    // 图片转base64地址
    var canvas = document.createElement('canvas');
    var context = canvas.getContext('2d');
    var width = domImg.natureWidth;
    var height = domImg.natureHeight;
    context.drawImage(domImg, 0, 0);
    // 如果是PNG图片，则context.toDataURL('image/png')
    eleLink.href = context.toDataURL('image/jpeg');
    // 触发点击
    document.body.appendChild(eleLink);
    eleLink.click();
    // 然后移除
    document.body.removeChild(eleLink);
};

　　

　　

转自 张鑫旭大神 https://www.zhangxinxu.com/wordpress/2017/07/js-text-string-download-as-html-json-file/