<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=Edge">
<meta content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no" name="viewport">
<title>js 文本 写入文件并下载</title>
</head>
<body>
<button type="button" id="btn">字符串格式转文件下载</button>
<button type="button" id="btn2">base64格式转文件下载</button>
</body>
<script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
<script>
var StringToBtye = {
stringToBytes(str) {
var bytes = new Array();
for (var i = 0; i < str.length; i++) {
var c = str.charCodeAt(i);
var s = parseInt(c).toString(2);
if (c >= parseInt("000080", 16) && c <= parseInt("0007FF", 16)) {
var af = "";
for (var j = 0; j < (11 - s.length); j++) {
af += "0";
}
af += s;
var n1 = parseInt("110" + af.substring(0, 5), 2);
var n2 = parseInt("110" + af.substring(5), 2);
if (n1 > 127) n1 -= 256;
if (n2 > 127) n2 -= 256;
bytes.push(n1);
bytes.push(n2);
} else if (c >= parseInt("000800", 16) && c <= parseInt("00FFFF", 16)) {
var af = "";
for (var j = 0; j < (16 - s.length); j++) {
af += "0";
}
af += s;
var n1 = parseInt("1110" + af.substring(0, 4), 2);
var n2 = parseInt("10" + af.substring(4, 10), 2);
var n3 = parseInt("10" + af.substring(10), 2);
if (n1 > 127) n1 -= 256;
if (n2 > 127) n2 -= 256;
if (n3 > 127) n3 -= 256;
bytes.push(n1);
bytes.push(n2);
bytes.push(n3);
} else if (c >= parseInt("010000", 16) && c <= parseInt("10FFFF", 16)) {
var af = "";
for (var j = 0; j < (21 - s.length); j++) {
af += "0";
}
af += s;
var n1 = parseInt("11110" + af.substring(0, 3), 2);
var n2 = parseInt("10" + af.substring(3, 9), 2);
var n3 = parseInt("10" + af.substring(9, 15), 2);
var n4 = parseInt("10" + af.substring(15), 2);
if (n1 > 127) n1 -= 256;
if (n2 > 127) n2 -= 256;
if (n3 > 127) n3 -= 256;
if (n4 > 127) n4 -= 256;
bytes.push(n1);
bytes.push(n2);
bytes.push(n3);
bytes.push(n4);
} else {
bytes.push(c & 0xff);
}
}
return bytes;
}
}
var file = new Uint8Array(StringToBtye.stringToBytes(JSON.stringify({ KEY: ‘12345678‘ }))).buffer;
console.log(file);
$(function () {
$("#btn").on(‘click‘, function () {
downloadTxt("hello.txt", "This is the content of my file");
})
$("#btn2").on(‘click‘, function () {
downloadByBlob("base64.txt");
})
})
//通过a标签指定文本格式和编码直接下载
function downloadTxt(fileName, content) {
let a = document.createElement(‘a‘);
a.href = ‘data:text/plain;charset=utf-8,‘ + content
a.download = fileName
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
}
//通过FileReader转化为base64字符串下载
function downloadByBlob(fileName) {
let blob = new Blob([file], {
type: "text/plain;base64"
});
let reader = new FileReader();
reader.readAsDataURL(blob);
reader.onload = function (e) {
let a = document.createElement(‘a‘);
a.download = fileName;
a.href = e.target.result;
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
}
}
</script>
</html>
原文：https://www.cnblogs.com/zhenguo-chen/p/13698294.html