First thanks for adding these nice array functions.

I played with, and it's not intuitive how to use.

Example merge:
var a = [1,2,3];
var b = [7,8,9];
var c = Ext.Array.merge(a,b);
Example indexOf:
var d = b.indexOf(8);
Would be helpful to have such mini examples included or hint how to use (Ext.Array or array prototype)