JavaScript Tutorial: Controlling the Timing of JavaScript's Execution

By: Dusty Arlia
Published on February 15, 2013
Last Updated on Monday, July 06, 2015 at 3:22 PM
Total Updates: 3

Your JavaScript running at the right time correlates to your JavaScript program being inserted at the right place in your HTML document. The browser executes JavaScript as it is encountered during the page-parsing process. This is why the order of your code is extremely important.

If your JavaScript program tries to use an HTML element that isn't loaded yet, then your JavaScript program will fail. So if your JavaScript program uses HTML elements in the page, make sure the JavaScript program is below that element in the HTML document or use a document loading method like JQuery's ready() or load() methods.

The problems related to your JavaScript program not running at the correct time can be sporadic. For instance, one time you view the page everything might be working ok, but the next time you might have a problem. This sporadicness can be attributed to varying network speeds and browser caching. Troubleshooting these issues can be difficult. It is always important to test your webpages with different web browsers in different environments.