gistfile1.js

// https://gist.github.com/Yaffle/1287361
var crc32table = null;
crc32 = function(s) {
    s = String(s);
    var polynomial = 0x04C11DB7,
        initialValue = 0xFFFFFFFF,
        finalXORValue = 0xFFFFFFFF,
        crc = initialValue,
        i, j, c;

    var buildTable = function() {
        var reverse = function (x, n) {
            var b = 0;
            while (n) {
                b = b * 2 + x % 2;
                x /= 2;
                x -= x % 1;
                n--;
            }
            return b;
        };

        crc32table = [];
        for (i = 255; i >= 0; i--) {
            c = reverse(i, 32);

            for (j = 0; j < 8; j++) {
                c = ((c * 2) ^ (((c >>> 31) % 2) * polynomial)) >>> 0;
            }

            crc32table[i] = reverse(c, 32);
        }
    };

    if( !crc32table )
        buildTable();


    for (i = 0; i < s.length; i++) {
        c = s.charCodeAt(i);
        if (c > 255) {
            throw new RangeError();
        }
        j = (crc % 256) ^ c;
        crc = ((crc / 256) ^ crc32table[j]) >>> 0;
    }

    return (crc ^ finalXORValue) >>> 0;
}


alert(crc32('test').toString(16));//D87F7E0C
alert(crc32('test', 0x04c11db7, 0, 0xFFFFFFFF).toString(16));//6C45EEF
alert(crc32('test', 0x04c11db7, 0xFFFFFFFF, 0).toString(16));//278081F3
alert(crc32('test', 0x04c11db7, 0, 0).toString(16));//F93BA110

Updated a tiny bit to only compute table on first execution