Is there a way to see which functions are being executed on a page?
If I load an external script on a page, is it possible to change what a function does on the fly or prevent it from running?
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3You can use your browser's developer tools.Oriol– Oriol2014-05-29 21:54:40 +00:00Commented May 29, 2014 at 21:54
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In practice this wouldn't be very useful, as there are often thousands of functions executing per second when things are actually happening.user229044– user229044 ♦2014-05-29 21:55:49 +00:00Commented May 29, 2014 at 21:55
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1codeschool.com/courses/discover-devtools is a free course about the developer tools in chrome. I think they're the best compared to other popular browsers, but it is a matter of personal preference.Will– Will2014-05-29 21:55:49 +00:00Commented May 29, 2014 at 21:55
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JavaScript is single threaded, so you cannot run other JS code in parallel to monitor other JS code. You'd need access to the engine if you wanted change its behavior.Felix Kling– Felix Kling2014-05-29 21:58:05 +00:00Commented May 29, 2014 at 21:58
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3 Answers
HTML5 introduces onbeforescriptexecute event, which you can use to detect new scripts on the fly, and block them if you want.
For example:
window.addEventListener('beforescriptexecute', function(e) {
// e.target.src is the URL of the external loaded script
// e.target.innerHTML is the content of the inline loaded script
if (e.target.src === urlToBlock)
e.preventDefault(); // Block script
}, true);
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Use Firebug for Firefox or Chrome Developer Tools. You can set the breakpoints and debug your code very well.
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https://developer.chrome.com/devtools/docs/javascript-debugging Here's a good place to start.