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AJAX and APIs
How can I make an AJAX call?
You can use any AJAX library you like with React. Some popular ones areAxios,jQuery AJAX, and the browser built-inwindow.fetch.
Where in the component lifecycle should I make an AJAX call?
You should populate data with AJAX calls in thecomponentDidMount lifecycle method. This is so you can usesetState to update your component when the data is retrieved.
Example: Using AJAX results to set local state
The component below demonstrates how to make an AJAX call incomponentDidMount to populate local component state.
The example API returns a JSON object like this:
{ "items": [ { "id": 1, "name": "Apples", "price": "$2" }, { "id": 2, "name": "Peaches", "price": "$5" } ] }classMyComponentextendsReact.Component{constructor(props){super(props);this.state={error:null,isLoaded:false,items:[]};}componentDidMount(){fetch("https://api.example.com/items").then(res=> res.json()).then((result)=>{this.setState({isLoaded:true,items: result.items});},// Note: it's important to handle errors here// instead of a catch() block so that we don't swallow// exceptions from actual bugs in components.(error)=>{this.setState({isLoaded:true, error});})}render(){const{ error, isLoaded, items}=this.state;if(error){return<div>Error:{error.message}</div>;}elseif(!isLoaded){return<div>Loading...</div>;}else{return(<ul>{items.map(item=>(<likey={item.id}>{item.name}{item.price}</li>))}</ul>);}}}Here is the equivalent withHooks:
functionMyComponent(){const[error, setError]=useState(null);const[isLoaded, setIsLoaded]=useState(false);const[items, setItems]=useState([]);// Note: the empty deps array [] means// this useEffect will run once// similar to componentDidMount()useEffect(()=>{fetch("https://api.example.com/items").then(res=> res.json()).then((result)=>{setIsLoaded(true);setItems(result);},// Note: it's important to handle errors here// instead of a catch() block so that we don't swallow// exceptions from actual bugs in components.(error)=>{setIsLoaded(true);setError(error);})},[])if(error){return<div>Error:{error.message}</div>;}elseif(!isLoaded){return<div>Loading...</div>;}else{return(<ul>{items.map(item=>(<likey={item.id}>{item.name}{item.price}</li>))}</ul>);}}Is this page useful?Edit this page