Аналоги PHP функций base64_decode и base64_encode

function base64_decode( data ) {
    var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    var o1, o2, o3, h1, h2, h3, h4, bits, i=0, enc='';

    do { 

        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)     enc += String.fromCharCode(o1);
        else if (h4 == 64) enc += String.fromCharCode(o1, o2);
        else               enc += String.fromCharCode(o1, o2, o3);

    } while (i < data.length);

    return enc;
}

function base64_encode( data ) {

    var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var o1, o2, o3, h1, h2, h3, h4, bits, i=0, enc='';
 
    do {
        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;
 
        enc += b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
    } while (i < data.length);
 
    switch( data.length % 3 ){
        case 1:
            enc = enc.slice(0, -2) + '=='; break;
        case 2:
            enc = enc.slice(0, -1) + '=';  break;
    }
 
    return enc;
}