How do I declare and use dynamic variables in JavaScript?

In JavaScript (as i know) there are 2 ways by which you can create dynamic variables:

1. eval Function
2. window object

eval:

var pageNumber = 1;
eval("var text" + pageNumber + "=123;");
alert(text1);

window object:

var pageNumber = 1;
window["text" + pageNumber] = 123;
alert(window["text" + pageNumber]);