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setState() does not always immediately update the component. It may batch or defer the update until later. This makes reading this.state right after calling setState() a potential pitfall. Instead, use componentDidUpdate or a setState callback (setState(updater, callback)), either of which are guaranteed to fire after the update has been applied.
can create the impression that instead of doing:
this.setState({value: 5});console.log(this.state.value);// => not necessarily 5
you can use the callback function to safely read the state back:
(especially if you draw a parallel between the callback function and the updater function)
and it may actually work in some cases where there's no setState batching, but as more calls get batched in the future, these constructs may generate unintended side-effects.
Instead, we could clarify that all callback functions for a batch of setState() calls get called after the entire batch has been processed.
The text was updated successfully, but these errors were encountered:
danburzo
changed the title
setState() callback function potential confusion of call order.
setState() callback function: potential confusion of call order
Mar 16, 2018
This paragraph from the React.Component reference page:
can create the impression that instead of doing:
you can use the callback function to safely read the state back:
(especially if you draw a parallel between the callback function and the updater function)
and it may actually work in some cases where there's no setState batching, but as more calls get batched in the future, these constructs may generate unintended side-effects.
Instead, we could clarify that all callback functions for a batch of
setState()
calls get called after the entire batch has been processed.The text was updated successfully, but these errors were encountered: