To block Javascript on all sites in Safari on your Mac, you can go to the Safari menu > Settings > Security and uncheck Enable JavaScript. On your iPhone, this setting is available under Settings ...

Disable JavaScript here to get rid of it in Google Chrome on Android. On the same page, you can tap Add Site Exception, type the URL, and hit Add to allow JavaScript to run on specific websites.

Of all the hats JavaScript can wear, its form-processing features are among the most sought and used. Learn how to use JavaScript for form processing, validation, and more.

To enable JavaScript, go into the Settings app on your iPhone, click "Safari," then "Advanced," and swipe the JavaScript button to the right so it appears green. Here's a full breakdown with pictures.