JS convBase

gistfile1.txt

    /**
     * Convert base.
     *
     * @param string number
     * @param string fromBase
     * @param string toBase
     *
     * @return string|integer
     */
    var convBase = function(number, fromBase, toBase) {
        if (fromBase == toBase)
            return number;

        var fromLen   = fromBase.length;
        var toLen     = toBase.length;
        var numberLen = number.length;
        var retval    = '';
        if (toBase === '0123456789') {
            var retvalNum = big(0);
            for (i = 1; i <= numberLen; i++) {
                retvalNum = retvalNum.plus(
                    big(fromBase.indexOf(number.charAt(i-1))).times(
                        big(fromLen).pow(numberLen-i)
                    )
                );
            }
            return retvalNum.toFixed();
        }
        var base10;
        if (fromBase !== '0123456789') {
            base10 = convBase(number, fromBase, '0123456789');
        } else {
            base10 = number;
        }
        if (base10 < toBase.length)
            return toBase.charAt(base10);

        while (base10 >= 1) {
            retval = toBase.charAt(big(base10).mod(toLen))+retval;
            base10 = big(base10).div(toLen);
        }
        return retval;
    };

http://php.net/manual/en/function.base-convert.php#106546

https://github.com/MikeMcl/big.js/