CODEWITHSUNDEEP
reactjs
Noitidart
Noitidart

Reputation: 37328

Why componentDidUpdate trigger when prevState/prevProps are same as this.state/this.props

I have a component, and its componentDidUpdate seems to trigger for no reason. It's a child component, has no state. Even though the prevProps and this.props are the exact same its triggering, is there any reason for this? I thought update should only trigger when there is a change in the props/state?

Upvotes: 1

Views: 3498

Answers (2)

wintvelt
wintvelt

Reputation: 14101

componentDidUpdate() is fired every time the parent component re-renders (and passes in new props). And in stateful components also whenever setState() is fired.

Even if old prevprops and this.props are exactly the same, componentDidUpdate() is still fired if the parent component re-renders.

If you want to prevent react to enter a render cycle, you should implement the shouldComponentUpdate() method, where you can compare new and old props.

Upvotes: 7

iofjuupasli
iofjuupasli

Reputation: 3873

update should only trigger when there is a change in the props/state

No, React renders to VirtualDOM everything each time. But then it updates only changed properties in real DOM.

To avoid that you can use PureRenderMixin or your custom comparation code in shouldComponentUpdate.

Upvotes: 3

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