JavaScript 实现 Base64 编码与解码完整示例

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>js base64加密解密</title>
</head>
<body>
<script>
// 创建Base64对象
var Base64 = {
 _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
 encode: function(e) {
  var t = "";
  var n, r, i, s, o, u, a;
  var f = 0;
  e = Base64._utf8_encode(e);
  while (f < e.length) {
   n = e.charCodeAt(f++);
   r = e.charCodeAt(f++);
   i = e.charCodeAt(f++);
   s = n >> 2;
   o = (n & 3) << 4 | r >> 4;
   u = (r & 15) << 2 | i >> 6;
   a = i & 63;
   if (isNaN(r)) {
    u = a = 64
   } else if (isNaN(i)) {
    a = 64
   }
   t = t + this._keyStr.charAt(s) + this._keyStr.charAt(o) + this._keyStr.charAt(u) + this._keyStr.charAt(a)
  }
  return t
 },
 decode: function(e) {
  var t = "";
  var n, r, i;
  var s, o, u, a;
  var f = 0;
  e=e.replace(/[^A-Za-z0-9+/=]/g,"");
  while (f < e.length) {
   s = this._keyStr.indexOf(e.charAt(f++));
   o = this._keyStr.indexOf(e.charAt(f++));
   u = this._keyStr.indexOf(e.charAt(f++));
   a = this._keyStr.indexOf(e.charAt(f++));
   n = s << 2 | o >> 4;
   r = (o & 15) << 4 | u >> 2;
   i = (u & 3) << 6 | a;
   t = t + String.fromCharCode(n);
   if (u != 64) {
    t = t + String.fromCharCode(r)
   }
   if (a != 64) {
    t = t + String.fromCharCode(i)
   }
  }
  t = Base64._utf8_decode(t);
  return t
 },
 _utf8_encode: function(e) {
  e = e.replace(/rn/g, "n");
  var t = "";
  for (var n = 0; n < e.length; n++) {
   var r = e.charCodeAt(n);
   if (r < 128) {
    t += String.fromCharCode(r)
   } else if (r > 127 && r < 2048) {
    t += String.fromCharCode(r >> 6 | 192);
    t += String.fromCharCode(r & 63 | 128)
   } else {
    t += String.fromCharCode(r >> 12 | 224);
    t += String.fromCharCode(r >> 6 & 63 | 128);
    t += String.fromCharCode(r & 63 | 128)
   }
  }
  return t
 },
 _utf8_decode: function(e) {
  var t = "";
  var n = 0;
  var r = c1 = c2 = 0;
  while (n < e.length) {
   r = e.charCodeAt(n);
   if (r < 128) {
    t += String.fromCharCode(r);
    n++
   } else if (r > 191 && r < 224) {
    c2 = e.charCodeAt(n + 1);
    t += String.fromCharCode((r & 31) << 6 | c2 & 63);
    n += 2
   } else {
    c2 = e.charCodeAt(n + 1);
    c3 = e.charCodeAt(n + 2);
    t += String.fromCharCode((r & 15) << 12 | (c2 & 63) << 6 | c3 & 63);
    n += 3
   }
  }
  return t
 }
}
// 定义字符串
var string = 'Hello World!';
// 加密
var encodedString = Base64.encode(string);
console.log(encodedString); // 输出: "SGVsbG8gV29ybGQh"
// 解密
var decodedString = Base64.decode(encodedString);
console.log(decodedString); // 输出: "Hello World!"
</script>
</body>
</html>