reactjs

ReactJS: Warning: setState(…): Cannot update during an existing state transition

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Looks like you’re accidentally calling the handleButtonChange method in your render method, you probably want to do onClick={() => this.handleButtonChange(false)} instead. If you don’t want to create a lambda in the onClick handler, I think you’ll need to have two bound methods, one for each parameter. In the constructor: this.handleButtonChangeRetour = this.handleButtonChange.bind(this, true); this.handleButtonChangeSingle = … Read more

How to use switch statement inside a React component?

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Try this, which is way cleaner too: Get that switch out of the render in a function and just call it passing the params you want. For example: renderSwitch(param) { switch(param) { case ‘foo’: return ‘bar’; default: return ‘foo’; } } render() { return ( <div> <div> // removed for brevity </div> {this.renderSwitch(param)} <div> // … Read more

React Hooks: useEffect() is called twice even if an empty array is used as an argument

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Put the console.log inside the useEffect Probably you have other side effects that cause the component to rerender but the useEffect itself will only be called once. You can see this for sure with the following code. useEffect(()=>{ /* Query logic */ console.log(‘i fire once’); },[]); If the log “i fire once” is triggered more … Read more

Sending the bearer token with axios

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const config = { headers: { Authorization: `Bearer ${token}` } }; const bodyParameters = { key: “value” }; Axios.post( ‘http://localhost:8000/api/v1/get_token_payloads’, bodyParameters, config ).then(console.log).catch(console.log); The first parameter is the URL. The second is the JSON body that will be sent along your request. The third parameter are the headers (among other things). Which is JSON as … Read more

react-router vs react-router-dom, when to use one or the other?

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react-router contains all the common components between react-router-dom and react-router-native. When should you use one over the other? If you’re on the web then react-router-dom should have everything you need as it also exports the common components you’ll need. If you’re using React Native, react-router-native should have everything you need for the same reason. So … Read more

React.Component vs React.PureComponent [closed]

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The major difference between React.PureComponent and React.Component is PureComponent does a shallow comparison on state change. It means that when comparing scalar values it compares their values, but when comparing objects it compares only references. It helps to improve the performance of the app. You should go for React.PureComponent when you can satisfy any of … Read more

Inline CSS styles in React: how to implement a:hover?

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I think onMouseEnter and onMouseLeave are the ways to go, but I don’t see the need for an additional wrapper component. Here is how I implemented it: var Link = React.createClass({ getInitialState: function(){ return {hover: false} }, toggleHover: function(){ this.setState({hover: !this.state.hover}) }, render: function() { var linkStyle; if (this.state.hover) { linkStyle = {backgroundColor: ‘red’} } … Read more

When to use React setState callback

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Yes there is, since setState works in an asynchronous way. That means after calling setState the this.state variable is not immediately changed. so if you want to perform an action immediately after setting state on a state variable and then return a result, a callback will be useful Consider the example below …. changeTitle: function … Read more

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