It would be inappropriate to have any chapter on client-side JavaScript without having a Hello, world!
example at some point.
ServiceNow has a very simple JavaScript executor that is the equivalent of Background Scripts, but for the browser. On almost any page, pressing Ctrl + Shift + J will launch the JavaScript execution window:
Let's run some code:
alert('Hello, world!');
Once you press the Run my code button, you should see the little pop-up alert box, as you may expect.
Your web browser executes the very simple JavaScript that you put in the window. Virtually every browser has a JavaScript console that provides the same functionality, which you will probably prefer, but it is helpful that ServiceNow gives you a simple alternative for every browser.