function download(filename, text) {
? var element = document.createElement('a');
? element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
? element.setAttribute('download', filename);
?
? element.style.display = 'none';
? document.body.appendChild(element);
?
? element.click();?
? document.body.removeChild(element);
}?
?
download("hello.txt","This is the content of my file :)");

var content = "What's up , hello world";
// any kind of extension (.txt,.cpp,.cs,.bat)
var filename = "hello.txt";
?
var blob = new Blob([content], {
?type: "text/plain;charset=utf-8"
});
?
saveAs(blob, filename);

<textarea name="" id="text" cols="30" rows="10">這里輸入的數(shù)據(jù)將保存為txt中</textarea>
<button id="save" type="button">保存</button>

? ? ? ?document.querySelector('#save').addEventListener('click', saveFile);
? ? ? ?function fakeClick(obj) {?
? ? ? ?　　var ev = document.createEvent("MouseEvents");
ev.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
　　　　obj.dispatchEvent(ev);
　　}
　　function exportRaw(name, data) {
　　　　var urlObject = window.URL || window.webkitURL || window;
　　　　var export_blob = new Blob([data]);
　　　　var save_link = document.createElementNS("http://www.w3.org/1999/xhtml", "a")
　　　　save_link.href = urlObject.createObjectURL(export_blob);
　　　　save_link.download = name;
　　　　fakeClick(save_link);
　　}
　　function saveFile(){
　　　　var inValue ?= document.querySelector('#text').value;
　　　　exportRaw('test.txt', inValue);
　　}