编码、转码、加密、解密的方法

escape("小星星")  // "%u5C0F%u661F%u661F"
escape("?!=()#%&") // "%3F%21%3D%28%29%23%25%26"

encodeURI("小星星") // "%E5%B0%8F%E6%98%9F%E6%98%9F"
decodeURIComponent("%E5%B0%8F%E6%98%9F%E6%98%9F") // "小星星"
decodeURI("%E5%B0%8F%E6%98%9F%E6%98%9F") // "小星星"

‘9‘.charCodeAt() // 57 把9转换成unicode编码值(数字57)

String.fromCharCode(97) // a 把unicode编码97转换成字符串a

<script>
  function base64EncodeChars() {
    return "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  }
  function base64DecodeChars() {
    var dataDeco = new Array(
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
      -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
      -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);
    return dataDeco;
  }
  function base64encode(str) {
    var out, i, len;
    var c1, c2, c3;
    len = str.length;
    i = 0;
    out = "";
    while (i < len) {
      c1 = str.charCodeAt(i++) & 0xff;
      if (i == len) {
        out += base64EncodeChars().charAt(c1 >> 2);
        out += base64EncodeChars().charAt((c1 & 0x3) << 4);
        out += "==";
        break;
      }
      c2 = str.charCodeAt(i++);
      if (i == len) {
        out += base64EncodeChars().charAt(c1 >> 2);
        out += base64EncodeChars().charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
        out += base64EncodeChars().charAt((c2 & 0xF) << 2);
        out += "=";
        break;
      }
      c3 = str.charCodeAt(i++);
      out += base64EncodeChars().charAt(c1 >> 2);
      out += base64EncodeChars().charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
      out += base64EncodeChars().charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));
      out += base64EncodeChars().charAt(c3 & 0x3F);
    }
    return out;
  }
  function base64decode(str) {
    var c1, c2, c3, c4;
    var i, len, out;
    len = str.length;
    i = 0;
    out = "";
    while (i < len) {
      do {
        c1 = base64DecodeChars()[str.charCodeAt(i++) & 0xff];
      } while (i < len && c1 == -1);
      if (c1 == -1)
        break;
      do {
        c2 = base64DecodeChars()[str.charCodeAt(i++) & 0xff];
      } while (i < len && c2 == -1);
      if (c2 == -1)
        break;
      out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
      do {
        c3 = str.charCodeAt(i++) & 0xff;
        if (c3 == 61)
          return out;
        c3 = base64DecodeChars()[c3];
      } while (i < len && c3 == -1);
      if (c3 == -1)
        break;
      out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
      do {
        c4 = str.charCodeAt(i++) & 0xff;
        if (c4 == 61)
          return out;
        c4 = base64DecodeChars()[c4];
      } while (i < len && c4 == -1);
      if (c4 == -1)
        break;
      out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
    }
    return out;
  }
  function utf16to8(str) {
    var out, i, len, c;
    out = "";
    len = str.length;
    for (i = 0; i < len; i++) {
      c = str.charCodeAt(i);
      if ((c >= 0x0001) && (c <= 0x007F)) {
        out += str.charAt(i);
      } else if (c > 0x07FF) {
        out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
        out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
        out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
      } else {
        out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
        out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
      }
    }
    return out;
  }
  function utf8to16(str) {
    var out, i, len, c;
    var char2, char3;
    out = "";
    len = str.length;
    i = 0;
    while (i < len) {
      c = str.charCodeAt(i++);
      switch (c >> 4) {
        case 0:
        case 1:
        case 2:
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
          // 0xxxxxxx
          out += str.charAt(i - 1);
          break;
        case 12:
        case 13:
          char2 = str.charCodeAt(i++);
          out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
          break;
        case 14:
          char2 = str.charCodeAt(i++);
          char3 = str.charCodeAt(i++);
          out += String.fromCharCode(((c & 0x0F) << 12) |
            ((char2 & 0x3F) << 6) |
            ((char3 & 0x3F) << 0));
          break;
      }
    }
    return out;
  }
  var Base64 = function () {
    return {
      encode: function (a) {
        return base64encode(utf16to8(a));
      },
      decode: function (a) {
        return utf8to16(base64decode(a));
      }
    }
  }();
  console.log(Base64.encode("小星星"), Base64.decode("5bCP5pif5pif")) // 调用方式
</script>