JavaScript写入文件到本地

　　⼯作中有时需要通过 JavaScript 保存⽂件到本地，我们都知道 JavaScript 基于安全的考虑，是不允许直接操作本地⽂件的。IE 可以通过 VB 插件的⽅式进⾏，⽽ Chrome 和 firefox 都不⽀持 JavaScript 向本地写⼊⽂件，所以 VB 插件的⽅式存在兼容性问题。那有没有适合的⽅法呢？答案是肯定的，我们可以通过 FileSaver.js 这个⼩插件实现我们的需求。下⾯看⼀段具体的代码吧：/**

* 下载⽂件 */

var downloadTextFile = function(mobileCode) { if(isEmpty(mobileCode)) { mobileCode = ''; }

var file = new File([mobileCode], \"⼿机号.txt\ saveAs(file);}

　　这个⽰例是向本地存储⼀个名字叫“⼿机号.txt”的⽂本⽂件，采⽤的字符编码格式为“UTF-8”，这样就避免的中⽂乱码的问题。聪明的你也赶快试试吧！

附 FileSaver.js ⽂件的完整源码：

/* FileSaver.js

* A saveAs() FileSaver implementation. * 1.3.2

* 2016-06-16 18:25:19 *

* 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 view === \"undefined\" || 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\ , can_use_save_link = \"download\" in save_link , click = function(node) {

var event = new MouseEvent(\"click\"); node.dispatchEvent(event); }

, is_safari = /constructor/i.test(view.HTMLElement) || view.safari , is_chrome_ios =/CriOS\\/[\\d]+/.test(navigator.userAgent) , throw_outside = function(ex) {

(view.setImmediate || view.setTimeout)(function() { throw ex; }, 0); }

, force_saveable_type = \"application/octet-stream\"

// the Blob API is fundamentally broken as there is no \"downloadfinished\" event to subscribe to , arbitrary_revoke_timeout = 1000 * 40 // 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(); } };

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)

// note: your browser will automatically convert UTF-16 U+FEFF to EF BB BF

if (/^\\s*(?:text\\/\\S*|application\\/xml|\\S*\\/\\S*\\+xml)\\s*;.*charset\\s*=\\s*utf-8/i.test(blob.type)) { return new Blob([String.fromCharCode(0xFEFF), 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

, force = type === force_saveable_type , object_url

, dispatch_all = function() {

dispatch(filesaver, \"writestart progress write writeend\".split(\" \")); }

// on any filesys errors revert to saving with object URLs , fs_error = function() {

if ((is_chrome_ios || (force && is_safari)) && view.FileReader) { // Safari doesn't allow downloading of blob urls var reader = new FileReader(); reader.onloadend = function() {

var url = is_chrome_ios ? reader.result : reader.result.replace(/^data:[^;]*;/, 'data:attachment/file;'); var popup = view.open(url, '_blank'); if(!popup) view.location.href = url;

url=undefined; // release reference before dispatching filesaver.readyState = filesaver.DONE; dispatch_all(); };

reader.readAsDataURL(blob);

filesaver.readyState = filesaver.INIT; return; }

// don't create more object URLs than needed if (!object_url) {

object_url = get_URL().createObjectURL(blob); }

if (force) {

view.location.href = object_url; } else {

var opened = view.open(object_url, \"_blank\"); if (!opened) {

// Apple does not allow window.open, see https://developer.apple.com/library/safari/documentation/Tools/Conceptual/SafariExtensionGuide/WorkingwithWindowsandTabs/WorkingwithWindowsand view.location.href = object_url; } }

filesaver.readyState = filesaver.DONE; dispatch_all(); revoke(object_url); } ;

filesaver.readyState = filesaver.INIT;

if (can_use_save_link) {

object_url = get_URL().createObjectURL(blob); setTimeout(function() {

save_link.href = object_url; save_link.download = name; click(save_link); dispatch_all(); revoke(object_url);

filesaver.readyState = filesaver.DONE; }); return; }

fs_error(); }

, FS_proto = FileSaver.prototype

, saveAs = function(blob, name, no_auto_bom) {

return new FileSaver(blob, name || blob.name || \"download\ } ;

// IE 10+ (native saveAs)

if (typeof navigator !== \"undefined\" && navigator.msSaveOrOpenBlob) { return function(blob, name, no_auto_bom) { name = name || blob.name || \"download\";

if (!no_auto_bom) {

blob = auto_bom(blob); }

return navigator.msSaveOrOpenBlob(blob, name); }; }

FS_proto.abort = function(){};

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 window

if (typeof module !== \"undefined\" && module.exports) { module.exports.saveAs = saveAs;

} else if ((typeof define !== \"undefined\" && define !== null) && (define.amd !== null)) { define(\"FileSaver.js\ return saveAs; });

}