Question

I work with some very large and confusing JavaScript files that I did not write. Sometimes an alert will come up but I don’t know where it’s coming from.

You could search all files for the text contained in the alert but if that text is dynamic it won’t work.

Is there a way to set a breakpoint in order to intercept an alert?

Answer 1

At the very top of your HTML:

window.alert = function() {
    debugger;
}

debugger is a statement that invokes any debugging functionality available. With developer tools open, you’ll automatically hit a breakpoint whenever alert is called. You can then inspect the call stack to see exactly what called the custom alert function.