• js解析base64


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    var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
         var base64DecodeChars = 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);
        //编码的方法
        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;
        }
        //解码的方法
        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:
               // 110x xxxx   10xx xxxx
               char2 = str.charCodeAt(i++);
               out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
               break;
             case 14:
               // 1110 xxxx  10xx xxxx  10xx xxxx
               char2 = str.charCodeAt(i++);
               char3 = str.charCodeAt(i++);
               out += String.fromCharCode(((c & 0x0F) << 12) |
                              ((char2 & 0x3F) << 6) |
                              ((char3 & 0x3F) << 0));
               break;
           }
           }
           return out;
      }

      调用方法:

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    //编码
     value = base64encode(utf16to8(src))
         
    //解码
    value = utf8to16(base64decode(src))
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  • 原文地址:https://www.cnblogs.com/gluncle/p/15814162.html
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