當用GET方式來實現檔案（excel、pdf、doc）匯出或下載的時候，傳參比較簡單直接放到url裡面，常用的匯出方法有：

1>window.open(url引數)，來實現檔案的匯出。

2>動態新增a標籤,<a target="_blank" href="url引數"></a>來實現檔案的匯出。

當使用post來實現檔案匯出或下載的時候傳參是一個問題，要知道不管是window.open還是a標籤只能get方式請求，在網上查找了關於用post實現傳參來匯出檔案或下載，然而並沒有合適的解決辦法。查了javascript權威指南結合自己的專案，找到了一種非常非常非常好的方法來實現檔案以GET方式匯出。長話短說，下面是解決方案：

所有瀏覽器都支援XMLHttpRequest物件（不瞭解的童鞋檢視javascript權威指南），它定義了用指令碼操作HTTP的API。這個API包含實現POST請求的能力。XHR2還定義了一種將URL指定的內容以Blob（二進位制）的形式下載下來。

例子：使用XMLHttpRequest下載Blob

function(){

};

xhr.send(params) //post請求傳的引數

}

那麼問題來了saveAs是個什麼東東呢，點選開啟連結簡而言支，有人貢獻了一份js來處理二進位制資料，裡面有個檔案FileSiver.js裡面的方法saveAs()來處理二進位制資料來實現檔案匯出。直接引用這個js檔案然後呼叫就行。

附saveAs()方法內容（重要哦）

/* FileSaver.js
 * A saveAs() FileSaver implementation.
 * 1.3.8
 * 2018-03-22 14:03:47
 *
 * By Eli Grey, https://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/src/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)
, setImmediate = view.setImmediate || view.setTimeout
, throw_outside = function(ex) {
setImmediate(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);
setImmediate(function() {
save_link.href = object_url;
save_link.download = name;
click(save_link);
dispatch_all();
revoke(object_url);
filesaver.readyState = filesaver.DONE;
}, 0);
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);
};
}


// todo: detect chrome extensions & packaged apps
//save_link.target = "_blank";


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
));