javascript中的Base64、UTF8编码与解码详解(2)

    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); 
    /**
     * base64编码
     * @param {Object} str
     */ 
    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; 
    } 
    /**
     * base64解码
     * @param {Object} str
     */ 
    function base64decode(str){ 
        var c1, c2, c3, c4; 
        var i, len, out; 
        len = str.length; 
        i = 0; 
        out = ""; 
        while (i < len) { 
            /* c1 */ 
            do { 
                c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; 
            } 
            while (i < len && c1 == -1); 
            if (c1 == -1)  
                break; 
            /* c2 */ 
            do { 
                c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; 
            } 
            while (i < len && c2 == -1); 
            if (c2 == -1)  
                break; 
            out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4)); 
            /* c3 */ 
            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)); 
            /* c4 */ 
            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; 
    } 
    /**
     * utf16转utf8
     * @param {Object} str
     */ 
    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; 
    } 
    /**
     * utf8转utf16
     * @param {Object} str
     */ 
    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 xxxx10xx xxxx10xx xxxx 
                    char2 = str.charCodeAt(i++); 
                    char3 = str.charCodeAt(i++); 
                    out += String.fromCharCode(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)); 
                    break; 
            } 
        } 
        return out; 
    } 
    //demo 
    //function doit(){ 
    //    var f = document.f; 
    //    f.output.value = base64encode(utf16to8(f.source.value)); 
    //    f.decode.value = utf8to16(base64decode(f.output.value)); 
    //} 

2.UTF8编码与解码：

复制代码 代码如下: