Trapping JavaScript Errors
On the other hand, MarsEdit features a rich HTML text editor largely implemented in JavaScript, a language which tends not to afford any of these convenient alerts to my mistakes. I have often stared in bewilderment as the editor window’s perplexing behavior, only to discover after many lost minutes or hours, that some subtle JavaScript error has been preventing the expected behavior of my code. I’ll switch to the WebKit inspector for the affected WebView, and discover the console is littered with red: errors being dutifully logged by the JavaScript runtime, but ignored by everybody.
Wouldn’t it be great if the JavaScript code crashed as hard as the Objective-C code does?
His solution is to add a JavaScript event listener that reports errors to the Objective-C delegate object.