CODEWITHSUNDEEP
javascriptreactjs
user11749059
user11749059

Reputation:

How to use Fetch queries in a loop?

I make a request to the server via a map with different urls, then I set the data in State and use it for output. I want the requests to be consecutive but sometimes they do not work correctly and get bugs, how to write the code for normal data retrieval?

const urlList = ["countries", "states", "cities", "users"];
componentDidMount() {
         urlList.map( (url, index) => {
            return servicesAPI.getResourse(url).then( (body) => {
                index !== 3 ?  this.setState({
                                 dataAPI : [...this.state.dataAPI, body] }) :
                                this.setState({
                                    dataAPI : [...this.state.dataAPI, body],
                                    loaded: true
                                })

            })
        })
export default  class ServicesAPI {
    _apiBase = `http://localhost:3001/`;


    async getResourse(url) {
        const res = await fetch(`${this._apiBase}${url}`);

        if (!res.ok) {
            throw new Error(`Could not fetch ${url}` +
                `, received ${res.status}`)
        }
        return await res.json();
    }

Upvotes: 2

Views: 199

Answers (1)

Andrei Todorut
Andrei Todorut

Reputation: 4526

Use of Promise.all();

componentDidMount() {
     const fetchPromises = [];
     urlList.forEach( (url, index) => {
        fetchPromises.push(servicesAPI.getResourse(url));
     });

     const allResourcesPromise = Promise.all(fetchPromises);
     allResourcesPromise.then(data => {
        // list with responses
     }).catch(err => {
        console.log(err.toString());
     });

}

Sample example: https://jsbin.com/vevufumano/1/edit?html,js,console,output

Also instead of then, where is possible, you can use async/await for more cleaner code.

Upvotes: 1

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