javascript hex to binary

function hex2bin(hexSource) {
    var bin = '';
    for (var i=0;i<hexSource.length;i=i+2) {
        bin += String.fromCharCode(hexdec(hexSource.substr(i,2)));
    }
    return bin;
}

function hexdec(hexString) {
    hexString = (hexString + '').replace(/[^a-f0-9]/gi, '')
    return parseInt(hexString, 16)
}