How to toggle boolean state of react component?

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I'd like to know how to toggle a boolean state of a react component. For instance:

I have boolean state check in the constructor of my component:

constructor(props, context) { 
   super(props, context);

   this.state = {
      check: false
   };
};

I am trying to toggle the state each time my checkbox is clicked, using the this.setState method:

<label><input type=checkbox" value="check" onChange = {(e) => this.setState({check: !check.value})}/> Checkbox </label>

Of course I get a Uncaught ReferenceError: check is not defined. So how can I achieve this?

Many thanks in advance.

Since nobody posted this, I am posting the correct answer. If your new state update depends on the previous state, always use the functional form of setState which accepts as argument a function that returns a new state.

In your case:

this.setState(prevState => ({
  check: !prevState.check
}));

See docs

Use State to Toggle an Element React - JavaScript, class MyComponent extends React.Component { constructor(props) { super(​props); this.state = { visibility: false }; // change code below this line this.​toggleVisibility  If would like to know how to toggle a boolean state of a react component? Since nobody posted this, I am posting the correct answer. If your new state update depends on the previous state, always use the functional form of setState which accepts as argument a function that returns a new state.

You should use this.state.check instead of check.value here:

this.setState({check: !this.state.check})

But anyway it is bad practice to do it this way. Much better to move it to separate method and don't write callbacks directly in markup.

How to toggle boolean state of react component?, If would like to know how to toggle a boolean state of a react component? Since nobody posted this, I am posting the correct answer. You want a toggle component that's simple and gives you complete control over rendering and state. This solution This follows the patterns in downshift to expose an API that renders nothing and simply encapsulates the logic of a toggle component.

Use checked to get the value. During onChange, checked will be true and it will be a type of boolean.

Hope this helps!

class A extends React.Component {
  constructor() {
    super()
    this.handleCheckBox = this.handleCheckBox.bind(this)
    this.state = {
      checked: false
    }
  }
  
  handleCheckBox(e) {
    this.setState({
      checked: e.target.checked
    })
  }
  
  render(){
    return <input type="checkbox" onChange={this.handleCheckBox} checked={this.state.checked} />
  }
}

ReactDOM.render(<A/>, document.getElementById('app'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

Best Practices for Component State in React.js, Store the simplest possible values to describe a component's state. In many cases, this means preferring the use of boolean flags. toggle 'active' in this.​state.classes when the component is clicked handleClick () { var  Managing State in Functional React Components with useState. As of React v16.7.0-alpha, function-based components have a lot more capability which includes the ability to manage state. In this post we are going to go through how we can use the Reacts useState function to manage state within a strongly-typed functional component with TypeScript.

Try:

<label><input type=checkbox" value="check" onChange = {(e) => this.setState({check: !this.state.check.value})}/> Checkbox </label>

Using check: !check.value means it is looking for the check object, which you haven't declared.

You need to specify that you want the opposite value of this.state.check.

ReactJS, We learnt this years ago, but it seems we need to re-learn it in React where for the API design of your React components can lead to bad decisions. this component manage its own state and handle its open/close status. Add an isHidden property to the component state; Trigger a function that toggles the isHidden value between true and false; Render the component when isHidden is false; React re renders a component each time the state changes, so you can add a conditional statement in the render function to display the component if isHidden is set to false.

Depending on your context; this will allow you to update state given the mouseEnter function. Either way, by setting a state value to either true:false you can update that state value given any function by setting it to the opposing value with !this.state.variable

state = {
  hover: false
}

onMouseEnter = () => {
  this.setState({
    hover: !this.state.hover
  });
};

How to Avoid the “Boolean Trap” When Designing React Components, Learn how to build a React switch component using the native HTML checkbox input! Long before iOS introduced the switch, the web's boolean input was component to keep track of the React switch component's state. If there’s one UI component that iOS introduced to the world, it’s the switch or toggle as some people refer to it as. What We’re Building. Building the React Switch Element using HTML. Styling our React Switch with CSS. Using the React Switch Component. Handling onChange and Passing a Value Through Props.

Build a React Switch Toggle Component, a demo React app that uses our custom toggle switch component. a boolean , and it determines the state of the toggle switch when it is  enabled - can be either a boolean or a function that returns a boolean, and it determines the state of the toggle switch when it is rendered. onStateChanged - is a callback function that will be called when the state of the toggle switch changes. This is useful for triggering actions on the parent component when the switch is toggled.

How To Build a Custom Toggle Switch with React, 8 Try REACTjs Tutorial - Toggle Content with State Playlist - https://www.youtube.​com/playlist Duration: 6:54 Posted: Jun 16, 2018 Whoa! By boiling the state concerns down to boolean values we must calculate the array of classes from within the render function; though, we also enhance the readability of the component. this.state.isHovering is a far better representation of the actual component state than this.state.classes.indexOf('hover') != -1. The component can be more

#8 Try REACTjs Tutorial - Toggle Content with State, All other values, including any object, an empty array ( [] ), or the string "false" , create an object with an initial value of true . Do not confuse the primitive Boolean​  All React Components must act like pure functions with respect to their props. This means functions that never try to change their inputs and always return the same result for the same inputs. This means functions that never try to change their inputs and always return the same result for the same inputs.

Comments
  • It's exactly as it says, check is undefined. You probably meant to write this.state.check in this.setState({check: !check.value}). And add the property checked for checkbox, which would change according to component state. checked={this.state.checked}
  • perfect implementation
  • why is this better than directly using this.setState({check: !this.state.check})?
  • @SunnyPro Read the linked docs and you shall find your answer. TL;DR is react optimizes calls to set state by batching them together. So imagine a simple increment function increment = () => this.setState({count: this.state.count + 1}); and a block of code: increment(); increment(); increment(); Now react may batch these into something analogous to: setNewState = (oldState) => { newState.count = oldState.count + 1; newState.count = oldState.count + 1; newState.count = oldState.count + 1; return newState; } See where the problem lies?
  • what if I need to update other state properties that aren't dependent on previous state at the same? For example togging a popover message, with visible as true/false but the message changing depending on state?
  • @hamncheez The return value of the function is your new state anyway. You may or may not use values from previous state; so you can send in any values, like different messages.
  • Upvoted, but out of curiosity - why is this "bad practice"?
  • It's better to separate view and logic because this way you will be able to see and update your logic and your markup separately and more easy.
  • This is not just bad practice, but you may not get the desired result, as setState is async. See my answer below.
  • I think Dane's answer has a better approach since it uses React's API meant to be used in case the new state depends on the previous state.
  • @MT. But then, I answered years later. There's that :)