Javascript中模拟PHP的base64_decode和base64_encode函数

PHP中的base64_decode和base64_encode函数不再是PHP的独享，而JS也可以使用这两个函数，下面把JS中的base64_decode和base64_encode函数贴出来，希望对需要的童鞋有所帮助~

javscript的base64_decode

function base64_decode (data) {    
    // *     example 1: base64_decode('S2V2aW4gdmFuIFpvbm5ldmVsZA==');
    // *     returns 1: 'Kevin van Zonneveld'  
 
    var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var o1, o2, o3, h1, h2, h3, h4, bits, i = 0, ac = 0, dec = "", tmp_arr = [];
 
    if (!data) {
        return data;
    }
 
    data += '';
 
    do {  // unpack four hexets into three octets using index points in b64
        h1 = b64.indexOf(data.charAt(i++));
        h2 = b64.indexOf(data.charAt(i++));
        h3 = b64.indexOf(data.charAt(i++));
        h4 = b64.indexOf(data.charAt(i++));
 
        bits = h1<<18 | h2<<12 | h3<<6 | h4;
 
        o1 = bits>>16 & 0xff;
        o2 = bits>>8 & 0xff;
        o3 = bits & 0xff;
 
        if (h3 == 64) {
            tmp_arr[ac++] = String.fromCharCode(o1);
        } else if (h4 == 64) {
            tmp_arr[ac++] = String.fromCharCode(o1, o2);
        } else {
            tmp_arr[ac++] = String.fromCharCode(o1, o2, o3);
        }
    } while (i < data.length);
 
    dec = tmp_arr.join('');
    dec = this.utf8_decode(dec);
 
    return dec;
}

javscript的base64_encode

function base64_encode (data) {
    // Encodes string using MIME base64 algorithm  
    // *     example 1: base64_encode('Kevin van Zonneveld');
    // *     returns 1: 'S2V2aW4gdmFuIFpvbm5ldmVsZA=='  
 
    var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var o1, o2, o3, h1, h2, h3, h4, bits, i = 0, ac = 0, enc="", tmp_arr = [];
 
    if (!data) {
        return data;
    }
 
    data = this.utf8_encode(data+'');
 
    do { // pack three octets into four hexets
        o1 = data.charCodeAt(i++);
        o2 = data.charCodeAt(i++);
        o3 = data.charCodeAt(i++);
 
        bits = o1<<16 | o2<<8 | o3;
 
        h1 = bits>>18 & 0x3f;
        h2 = bits>>12 & 0x3f;
        h3 = bits>>6 & 0x3f;
        h4 = bits & 0x3f;
 
        // use hexets to index into b64, and append result to encoded string
        tmp_arr[ac++] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
    } while (i < data.length);
 
    enc = tmp_arr.join('');
 
    switch (data.length % 3) {
        case 1:
            enc = enc.slice(0, -2) + '==';
        break;
        case 2:
            enc = enc.slice(0, -1) + '=';
        break;
    }
 
    return enc;
}