Not all browsers have JavaScript. Some non-visual browsers won’t use it. And you cannot rely on JavaScript existing even in visual browsers. Even if the viewer leaves JavaScript turned on in their browser, there’s a very good chance that some functionality will be turned off. Mostly, this is because JavaScript is commonly abused by scammers.
Many people have pop-up blocking turned on, for example, so that they don’t get advertisements popping up on their computer; most browsers have this option built-in because the problem is so widespread.
Some browsers let the visitor choose exactly what JavaScript functionality to allow, from the ability to resize windows on.
When going over this tutorial in early 2007, I discovered that the very simple first example didn’t function at all in two out of three of the then-major browsers. I’d chosen setting the text in the status bar as the first example because it required only a single line and because its result was so obvious. No longer; most likely the functionality was abused by phishing sites. As far as I can tell, the ability to see changed status text is no longer available in most browsers.
Browsers will also attempt to detect whether your script is consuming too many resources on the client computer. If the browser detects this, it will either automatically stop your script, or present the viewer with a dire warning that the script is likely doing something wrong, and do they want to cancel? Most likely they will.
Related Pages
