A.downloadHTML5的A标签有一个download属性，可以告诉浏览器下载而非预览文件，很实用，参考链接：http://www.zhangxinxu.com/wordpress/2016/0
A.download
HTML5的A标签有一个download属性，可以告诉浏览器下载而非预览文件，很实用，参考链接：http://www.zhangxinxu.com/wordpress/2016/04/know-about-html-download-attribute/
有时候，WEB端临时创建了一个文件，供用户下载，怎么办呢？示例如下：
// 从canvas提取图片数据var raw = ctx.getImageData(0, 0, 300, 300);// 压缩为JPEG图片// https://github.com/owencm/javascript-jpeg-encodervar jpegURI = (new JPEGEncoder()).encode(raw, 75);// 弹出对话框，交由用户保存图片saveFile(jpegURI, '文件名');// saveFile函数function saveFile(d, a) { var b = document.createElement('a'); b.href = d; b.download = a; var c = document.createEvent("MouseEvents"); c.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null); b.dispatchEvent(c);}FileSaver.js
这是另一种方案，效果也不错。这里推荐FileSaver.js修改版。
这里还有一段原作者的博文。
最后，贴出JS便于查看：
/* FileSaver.js * A saveAs() FileSaver implementation. * 1.1.20151003 * * By Eli Grey, http://eligrey.com * License: MIT * See https://github.com/eligrey/FileSaver.js/blob/master/LICENSE.md *//*global self *//*jslint bitwise: true, indent: 4, laxbreak: true, laxcomma: true, smarttabs: true, plusplus: true *//*! @source http://purl.eligrey.com/github/FileSaver.js/blob/master/FileSaver.js */var saveAs = saveAs || (function(view) { "use strict"; // IE <10 is explicitly unsupported if (typeof navigator !== "undefined" && /MSIE [1-9]/./.test(navigator.userAgent)) { return; } var doc = view.document // only get URL when necessary in case Blob.js hasn't overridden it yet , get_URL = function() { return view.URL || view.webkitURL || view; } , save_link = doc.createElementNS("http://www.w3.org/1999/xhtml", "a") , can_use_save_link = "download" in save_link , click = function(node) { var event = new MouseEvent("click"); node.dispatchEvent(event); } , is_safari = /Version//[/d/.]+.*Safari/.test(navigator.userAgent) , webkit_req_fs = view.webkitRequestFileSystem , req_fs = view.requestFileSystem || webkit_req_fs || view.mozRequestFileSystem , throw_outside = function(ex) { (view.setImmediate || view.setTimeout)(function() { throw ex; }, 0); } , force_saveable_type = "application/octet-stream" , fs_min_size = 0 // See https://code.google.com/p/chromium/issues/detail?id=375297#c7 and // https://github.com/eligrey/FileSaver.js/commit/485930a#commitcomment-8768047 // for the reasoning behind the timeout and revocation flow , arbitrary_revoke_timeout = 500 // in ms , revoke = function(file) { var revoker = function() { if (typeof file === "string") { // file is an object URL get_URL().revokeObjectURL(file); } else { // file is a File file.remove(); } }; if (view.chrome) { revoker(); } else { setTimeout(revoker, arbitrary_revoke_timeout); } } , dispatch = function(filesaver, event_types, event) { event_types = [].concat(event_types); var i = event_types.length; while (i--) { var listener = filesaver["on" + event_types[i]]; if (typeof listener === "function") { try { listener.call(filesaver, event || filesaver); } catch (ex) { throw_outside(ex); } } } } , auto_bom = function(blob) { // prepend BOM for UTF-8 XML and text/* types (including HTML) if (/^/s*(?:text///S*|application//xml|/S*///S*/+xml)/s*;.*charset/s*=/s*utf-8/i.test(blob.type)) { return new Blob(["/ufeff", blob], {type: blob.type}); } return blob; } , FileSaver = function(blob, name, no_auto_bom) { if (!no_auto_bom) { blob = auto_bom(blob); } // First try a.download, then web filesystem, then object URLs var filesaver = this , type = blob.type , blob_changed = false , object_url , target_view , dispatch_all = function() { dispatch(filesaver, "writestart progress write writeend".split(" ")); } // on any filesys errors revert to saving with object URLs , fs_error = function() { if (target_view && is_safari && typeof FileReader !== "undefined") { // Safari doesn't allow downloading of blob urls var reader = new FileReader(); reader.onloadend = function() { var base64Data = reader.result; target_view.location.href = "data:attachment/file" + base64Data.slice(base64Data.search(/[,;]/)); filesaver.readyState = filesaver.DONE; dispatch_all(); }; reader.readAsDataURL(blob); filesaver.readyState = filesaver.INIT; return; } // don't create more object URLs than needed if (blob_changed || !object_url) { object_url = get_URL().createObjectURL(blob); } if (target_view) { target_view.location.href = object_url; } else { var new_tab = view.open(object_url, "_blank"); if (new_tab == undefined && is_safari) { //Apple do not allow window.open, see http://bit.ly/1kZffRI view.location.href = object_url } } filesaver.readyState = filesaver.DONE; dispatch_all(); revoke(object_url); } , abortable = function(func) { return function() { if (filesaver.readyState !== filesaver.DONE) { return func.apply(this, arguments); } }; } , create_if_not_found = {create: true, exclusive: false} , slice ; filesaver.readyState = filesaver.INIT; if (!name) { name = "download"; } if (can_use_save_link) { object_url = get_URL().createObjectURL(blob); save_link.href = object_url; save_link.download = name; setTimeout(function() { click(save_link); dispatch_all(); revoke(object_url); filesaver.readyState = filesaver.DONE; }); return; } // Object and web filesystem URLs have a problem saving in Google Chrome when // viewed in a tab, so I force save with application/octet-stream // http://code.google.com/p/chromium/issues/detail?id=91158 // Update: Google errantly closed 91158, I submitted it again: // https://code.google.com/p/chromium/issues/detail?id=389642 if (view.chrome && type && type !== force_saveable_type) { slice = blob.slice || blob.webkitSlice; blob = slice.call(blob, 0, blob.size, force_saveable_type); blob_changed = true; } // Since I can't be sure that the guessed media type will trigger a download // in WebKit, I append .download to the filename. // https://bugs.webkit.org/show_bug.cgi?id=65440 if (webkit_req_fs && name !== "download") { name += ".download"; } if (type === force_saveable_type || webkit_req_fs) { target_view = view; } if (!req_fs) { fs_error(); return; } fs_min_size += blob.size; req_fs(view.TEMPORARY, fs_min_size, abortable(function(fs) { fs.root.getDirectory("saved", create_if_not_found, abortable(function(dir) { var save = function() { dir.getFile(name, create_if_not_found, abortable(function(file) { file.createWriter(abortable(function(writer) { writer.onwriteend = function(event) { target_view.location.href = file.toURL(); filesaver.readyState = filesaver.DONE; dispatch(filesaver, "writeend", event); revoke(file); }; writer.onerror = function() { var error = writer.error; if (error.code !== error.ABORT_ERR) { fs_error(); } }; "writestart progress write abort".split(" ").forEach(function(event) { writer["on" + event] = filesaver["on" + event]; }); writer.write(blob); filesaver.abort = function() { writer.abort(); filesaver.readyState = filesaver.DONE; }; filesaver.readyState = filesaver.WRITING; }), fs_error); }), fs_error); }; dir.getFile(name, {create: false}, abortable(function(file) { // delete file if it already exists file.remove(); save(); }), abortable(function(ex) { if (ex.code === ex.NOT_FOUND_ERR) { save(); } else { fs_error(); } })); }), fs_error); }), fs_error); } , FS_proto = FileSaver.prototype , saveAs = function(blob, name, no_auto_bom) { return new FileSaver(blob, name, no_auto_bom); } ; // IE 10+ (native saveAs) if (typeof navigator !== "undefined" && navigator.msSaveOrOpenBlob) { return function(blob, name, no_auto_bom) { if (!no_auto_bom) { blob = auto_bom(blob); } return navigator.msSaveOrOpenBlob(blob, name || "download"); }; } FS_proto.abort = function() { var filesaver = this; filesaver.readyState = filesaver.DONE; dispatch(filesaver, "abort"); }; FS_proto.readyState = FS_proto.INIT = 0; FS_proto.WRITING = 1; FS_proto.DONE = 2; FS_proto.error = FS_proto.onwritestart = FS_proto.onprogress = FS_proto.onwrite = FS_proto.onabort = FS_proto.onerror = FS_proto.onwriteend = null; return saveAs;}( typeof self !== "undefined" && self || typeof window !== "undefined" && window || this.content));// `self` is undefined in Firefox for Android content script context// while `this` is nsIContentFrameMessageManager// with an attribute `content` that corresponds to the windowif (typeof module !== "undefined" && module.exports) { module.exports.saveAs = saveAs;} else if ((typeof define !== "undefined" && define !== null) && (define.amd != null)) { define([], function() { return saveAs; });}