You can use here both input controls below to test your Regular Expressions. They are a powerful tool with a rather cryptic syntax, whence the need for this small tool. The first input control must contain the pattern you want to use. Click on Pattern to register it. The title of the button will change to reflect your input. In the second input control, type a string to be matched to that pattern. Click on Test, and if the string does match, the result will be true, otherwise false. If you want to know more about these expressions, click on the link above.
Example: Type 2+2, click on Alert+Eval (or type Enter on IExplorer), and you will see a popup with the result (4). If you type on the button Eval, you will need to explicitly add the alert() command to see something. Example: type alert(2+2); and click on Eval.
Example: Type document.getElementById('container').style.backgroundColor="silver" to change the page background color to silver. You can also call user-defined functions: try mySetRandomColor(); to randomly change the background color. Best of all, do the same with mySetRandomColor (without the parenthesis) to see the function source code!