Question

I’m finding that with asynchronous callbacks I’m needing to write a try/catch for each callback function. It seems a bit error prone is there a method or technique whereby I can implement a single top level try/catch that catches everything? If not is the technique that I’m using considered good practice or is there a better way to do things?

Answer 1

There is two ways of doing this:

1. Set the window’s onerror attribute
   • called with three arguments (message, url, lineNumber)
   • returning true(!) prevents the default error handling (making this something like a catch-all)
2. Add an error event listener to window
   • called with an Error event e as its sole argument
   • Calling e.preventDefault() prevents default error handling

If not is the technique that I’m using considered good practice or is there a better way to do things?

Due to the dynamic nature of JavaScript, try/catch is very slow. There’s almost always better ways, for example: check if something exists before calling a method on it.

// bad
try {
    document.getElementById('foo').focus();
} catch(e) {
    alert('foo not found');
}

//good
var el = document.getElementById('foo');
if (el) {
    el.focus();
} else {
    alert('foo not found');
}

For your specific situation, please show some of your code; maybe in a separate question.