‘events’ is null or not an object

If you work a lot with ExtJS, you’ve probably seen this error before when running IE. It presents itself as the yellow flag of doom at the bottom left of your IE browser, and can really ruin your mood. I can’t tell you how many hours I spent with IE8 debugger “tool” trying to figure out why this error kept displaying. This is one of the most cryptic & misleading errors I’ve ever seen.

9 times out of 10, the first thing you should look for is an extra comma!

You’ll likely find it hidden somewhere in a JS Object/Array definition, something like:

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var aQuickObject = {
  properties: [
    { property: 'value' },
    { property: 'value' },
  ]
};

What bugs me about this is that, afaik, IE is the only browser which has this problem. Chrome/Firefox are much less strict with extra commas, so you must always be on the lookout. A great tool to help finding extra commas and other syntactic errors is JSLint.

Tools aside, nothing beats the well-trained eye and clean coding practice!