Using array.push() inside my own array method gives error (JavaScript) : I have this code example:

    function s () {
	    this.func = [];
        this.func.addF = function (str) {
  	        this.func.push(str);
        }
    }

When I create an Instance of that object:

    var a = new s ();
    a.func.addF ("hello");

I get an error saying: **Uncaught TypeError: Cannot read property 'push' of undefined**.

I can understand that `this.func` is undefined at that point, but what should I do to make this work. Pls help.