FileSaver.js 瀏覽器匯出Excel檔案

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限制一：不同瀏覽器對 blob 對象有不同的限制

具體看看下面這個表格（出自 FileSaver.js）：

Browser	Constructs as	Filenames	Max Blob Size	Dependencies
Firefox 20+	Blob	Yes	800 MiB	None
Firefox < 20	data: URI	No	n/a	Blob.js
Chrome	Blob	Yes	500 MiB	None
Chrome for Android	Blob	Yes	500 MiB	None
Edge	Blob	Yes	?	None
IE 10+	Blob	Yes	600 MiB	None
Opera 15+	Blob	Yes	500 MiB	None
Opera < 15	data: URI	No	n/a	Blob.js
Safari 6.1+*	Blob	No	?	None
Safari < 6	data: URI	No	n/a	Blob.js

限制二：構建完 blob 對象後才會轉換成檔案

這一點限制對小檔案(幾十kb)可能沒什麼影響，但對稍微大一點的檔案影響就很大了。試想，使用者要下載一個 100mb 的檔案，如果他點擊了下載按鈕之後沒看到下載提示的話，他肯定會繼續按，等他按了幾次之後還沒看到下載提示時，他就會抱怨我們的網站，然後離開了。

然而事實上下載的的確確發生了，只是要等到下載完檔案之後才能構建 blob 對象，再轉化成檔案。而且，使用者再觸發多幾次下載就會造成一些資源上的浪費。

因此，如果是要下載大檔案的話，還是推薦直接建立一個 <a> 標籤拉~
寫 html 也好，寫 JavaScript 動態建立也好，用自己喜歡的方式去建立就好了。

FileSaver.js

/* 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", "a")        , 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/WorkingwithWindowsandTabs.html                            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", no_auto_bom);        }    ;    // 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 windowif (typeof module !== "undefined" && module.exports) {  module.exports.saveAs = saveAs;} else if ((typeof define !== "undefined" && define !== null) && (define.amd !== null)) {  define("FileSaver.js", function() {    return saveAs;  });}

調用方法

 function expToExcel(){            var content = $("#report").html();            var blob = new Blob(["Hello, world!"], { type: "text/plain;charset=utf-8" });            saveAs(blob, "hello world.txt");                    }

 

FileSaver.js 瀏覽器匯出Excel檔案