<script src="//jdataview.github.io/dist/jdataview.js"></script>
<script src="//jdataview.github.io/dist/jbinary.js"></script>
<script>
var typeSet = {
  magic: ['array', 'uint8', 4]
};
jBinary.load('file.bin', typeSet, function (err, binary) {
  console.log(binary.read('magic'));
});
</script>