How to get spread operator updating state with React

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I've defined my initial state in a Component as follows:

constructor(props) {
    super(props);
    //this.state = {count: props.initialCount};
    this.state = {
        timeArray: [],
        metawords: '',
        description: '',
        currentTime: '',
        inputFieldsDisabled: true
    }
}

I have an event that gets called and I want to just update the metawords property. I was thinking that the following code should work but it does not.

updateInputValue1(evt) {
    const newMetawords = "abcd";
    this.setState(
        [...this.state,{
            metawords: evt.target.value
        }]
    );

Thoughts?


state is an object so updating it the way you are at the moment won't work.

You can simply update only the property you need as:

this.setState({
  metawords: evt.target.value,
})

Since you've mentioned spread operator, you can also (but not always necessary) update your state as:

this.setState({
  ...this.state,
  metawords: evt.target.value,
})

or

this.setState(prevState => ({
  ...prevState,
  metawords: evt.target.value,
}))

Should you need more info about it, I recommend you to have a look at ReactJS documentation.

How to get spread operator updating state with React, You don't need to pass all other state values, just pass the property and the new value, that you want to update. You don't need to bother about the other state values during setState, React will do the merging (merging of all other state values and the state that you wants to update). Using the spread operator in React setState. I’m currently building an app using React.js and ran into an issue that had me stumped. When a button in the app is clicked, I needed a piece of the state to be updated. Sounds easy enough. The trick here though is that this particular piece of state is an array of objects.


You can use spread operator like this to setState.

this.setState(
        {...this.state,
          metawords: evt.target.value
        })

However since you only want to change a single property, this will also work in your case:

this.setState({metawords: evt.target.value})

ES6 Spread Operator in React by Example: Props and setState , in many React code examples which may have confused you. In fact You can use the ES6 Spread operator to pass props to a React Let's suppose, you need to use the setState() method to update your component state. React setState() with prevState and Object Spread Operator. There are some gotchas with React's setState(). For example, state updates may be asynchronous: React sometimes batches multiple setState() calls for performance reasons. Make sure to set state correctly and to use the latest state.


Why not simply:

this.setState({ metawords: evt.target.value })

You don't need to pass all other state values, just pass the property and the new value, that you want to update. You don't need to bother about the other state values during setState, React will do the merging (merging of all other state values and the state that you wants to update).

For more details check DOC.

React setState() with prevState and Object Spread Operator , For example, state updates may be asynchronous: React sometimes batches multiple setState() calls for performance reasons. Make sure to  In fact, this syntax is part of ES6 and not React itself and it's used by two operators - the Spread and Rest operators. The Spread operator lets you expand an iterable like a string, object or array into its elements while the Rest operator does the inverse by reducing a set of elemnts into one array.


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