javascript - What is the default implementation for "shouldComponentUpdate" lifecycle method in React componen

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A custom implementation for the shouldComponentUpdate() method as part of the React ponent lifecycle is not required.

I understand it's a boolean function that determines whether render() will be called upon changes in ponent props and state, and there are mixins like PureRenderMixin which implements the shouldComponentUpdate()

If no custom implementation nor mixins are provided. What's the default implementation and behavior?

A custom implementation for the shouldComponentUpdate() method as part of the React ponent lifecycle is not required.

I understand it's a boolean function that determines whether render() will be called upon changes in ponent props and state, and there are mixins like PureRenderMixin which implements the shouldComponentUpdate()

If no custom implementation nor mixins are provided. What's the default implementation and behavior?

• javascript
• reactjs

Share Improve this question Follow edited Nov 1, 2015 at 20:35 mu is too short 435k7171 gold badges859859 silver badges818818 bronze badges asked Nov 1, 2015 at 20:07 Ling ZhongLing Zhong 1,80411 gold badge1515 silver badges2424 bronze badges 1

• As I understand it, the ponent renders if you don't implement this function. The function is provided to let you fine tune the rendering mechanism for special cases. – davestevens Commented Nov 1, 2015 at 20:13

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3 Answers 3

Sorted by: Reset to default 6

As of React v0.13 and v0.14 the default implementation equals to null and as per this logic:

    var shouldUpdate =
      this._pendingForceUpdate ||
      !inst.shouldComponentUpdate ||
      inst.shouldComponentUpdate(nextProps, nextState, nextContext);

the ponent is updated every render cycle (since !inst.shouldComponentUpdate evaluates to true).

Defaults to true.

The default behaviour is to re-render on every state change, and in the vast majority of cases, you should rely on the default behaviour.

shouldComponentUpdate() is invoked before rendering when new props or state are being received. Defaults to true. This method is not called for the initial render or when forceUpdate() is used.

Given the documentation React Docs the default is true:

shouldComponentUpdate() is invoked before rendering when new props or state are being received. Defaults to true.

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