var n1 = 9;
var n2 = 2;
document.write(n1 + " = " + n1.toString(2) + "<br />");
document.write(n2 + " = " + n2.toString(2) + "<br />");
var x = n1 & n2;
document.write(x + " = " + x.toString(2) + "<br />");
/*
1001
& 0010
----
0000
*/
/*
run:
9 = 1001
2 = 10
0 = 0
*/