js工具类方法-base64编解码_base64465n459js-优快云博客

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原文： https://blog.youkuaiyun.com/crazy_victor/article/details/84869132

// base64 
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 = 0;
    var c1 = 0;
    var c2 = 0;
    var c3 = 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
  }
}