state react
class Example extends React.Component {
constructor(props) {
super(props);
this.state = {
count: 0
};
}
render() {
return (
<div>
<p>You clicked {this.state.count} times</p>
<button onClick={() => this.setState({ count: this.state.count + 1 })}>
Click me
</button>
</div>
);
}
}how to update state in react
// Correct
this.setState(function(state, props) {
return {
counter: state.counter + props.increment
};
});react setState
incrementCount() {
// Note: this will *not* work as intended.
this.setState({count: this.state.count + 1});
}
handleSomething() {
// Let's say `this.state.count` starts at 0.
this.incrementCount();
this.incrementCount();
this.incrementCount();
// When React re-renders the component, `this.state.count` will be 1, but you expected 3.
// This is because `incrementCount()` function above reads from `this.state.count`,
// but React doesn't update `this.state.count` until the component is re-rendered.
// So `incrementCount()` ends up reading `this.state.count` as 0 every time, and sets it to 1.
// The fix is described below!
}how to update state.item[1] in state using setState? React
handleChange: function (e) {
// 1. Make a shallow copy of the items
let items = [...this.state.items];
// 2. Make a shallow copy of the item you want to mutate
let item = {...items[1]};
// 3. Replace the property you're intested in
item.name = 'newName';
// 4. Put it back into our array. N.B. we *are* mutating the array here, but that's why we made a copy first
items[1] = item;
// 5. Set the state to our new copy
this.setState({items});
},update state in react
You have to use setState() for updating state in React
{
hasBeenClicked: false,
currentTheme: 'blue',
}
setState({
hasBeenClicked: true
});reactjs update state example
You have to use setState() for updating state in React
{
hasBeenClicked: false,
currentTheme: 'blue',
}
setState({
hasBeenClicked: true
});Copyright © 2021 Codeinu
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