How to combine two same lengths array into one same length array with element joined by a separator

Given

a=["a", "b", "c"];
x=["x", "y", "z"];

combine/join the two list: the expected result:

ax=["a:x", "b:y", "c:z"];

How?

Thanks

var ax = [];
for (var i = 0; i < a.length; i++) {
    ax.push(a[i] + ":" + x[i]);
}