TypeError: null is not an object

[zoltantothcom]

TypeError: null is not an object

[zoltantothcom]

It's weird because clampLines() with this.element is being called on componentDidMount() and a ref already should have been passed around according to React lifecycle diagram:

[digigarlab]

Regarding at the code, the only way I could see this happening is after a component unmount.

In the componentDidUnmount, the listener is removed, but there could be a debounced call still on the event loop at this stage, that would be executed after the component is actually unmounted.

From react doc:

React will assign the current property with the DOM element when the component mounts, and assign it back to null when it unmounts. ref updates happen before componentDidMount or componentDidUpdate lifecycle methods.

[digigarlab]

I don't have much time to test that assumption right now, but assuming it is, the fix would be to either:

• Ensure the component is still mounted before executing the func.apply in the debounced callback
• Just check for this.element nullity in the clampLines function

[zoltantothcom]

Thank you for your time and suggestion. This should be fixed now by

if (!this.element) return;

in clampLines()