How to make a rest post call from ReactJS code?

Straight from the React Native docs:

fetch('https://mywebsite.example/endpoint/', {
  method: 'POST',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    firstParam: 'yourValue',
    secondParam: 'yourOtherValue',
  })
})

(This is posting JSON, but you could also do, for example, multipart-form.)

Also see docs for ReactJS AJAX FAQs if not using React Native.

React doesn't really have an opinion about how you make REST calls. Basically you can choose whatever kind of AJAX library you like for this task.

The easiest way with plain old JavaScript is probably something like this:

var request = new XMLHttpRequest();
request.open('POST', '/my/url', true);
request.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
request.send(data);

In modern browsers you can also use fetch.

If you have more components that make REST calls it might make sense to put this kind of logic in a class that can be used across the components. E.g. RESTClient.post(…)

Another recently popular packages is : axios

Install : npm install axios --save

Simple Promise based requests

axios.post('/user', {
    firstName: 'Fred',
    lastName: 'Flintstone'
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  });

you can install superagent

npm install superagent --save

then for make post call to server

import request from "../../node_modules/superagent/superagent";

request
.post('http://localhost/userLogin')
.set('Content-Type', 'application/x-www-form-urlencoded')
.send({ username: "username", password: "password" })
.end(function(err, res){
console.log(res.text);
});  

As of 2018 and beyond, you have a more modern option which is to incorporate async/await in your ReactJS application. A promise-based HTTP client library such as axios can be used. The sample code is given below:

import axios from 'axios';
...
class Login extends Component {
    constructor(props, context) {
        super(props, context);
        this.onLogin = this.onLogin.bind(this);
        ...
    }
    async onLogin() {
        const { email, password } = this.state;
        try {
           const response = await axios.post('/login', { email, password });
           console.log(response);
        } catch (err) {
           ...
        }
    }
    ...
}

I think this way also a normal way. But sorry, I can't describe in English ((

    submitHandler = e => {
    e.preventDefault()
    console.log(this.state)
    fetch('http://localhost:5000/questions',{
        method: 'POST',
        headers: {
            Accept: 'application/json',
                    'Content-Type': 'application/json',
        },
        body: JSON.stringify(this.state)
    }).then(response => {
            console.log(response)
        })
        .catch(error =>{
            console.log(error)
        })
    
}

https://googlechrome.github.io/samples/fetch-api/fetch-post.html

fetch('url/questions',{ method: 'POST', headers: { Accept: 'application/json', 'Content-Type': 'application/json', }, body: JSON.stringify(this.state) }).then(response => { console.log(response) }) .catch(error =>{ console.log(error) })

Here is a the list of ajax libraries comparison based on the features and support. I prefer to use fetch for only client side development or isomorphic-fetch for using in both client side and server side development.

For more information on isomorphic-fetch vs fetch

import React, {useState} from 'react';
import Axios from 'axios';

export  default function Formlp() 
{
  const url ="";
  const [state, setstate] = useState({
    name:"",
    iduser:""
  })

  function handel(e){
    const newdata={...state}
    newdata[e.target.id]=e.target.value
    setstate(newdata);
  }

  function submit(e)
  {
    e.preventDefault();
    //Axios.post(url,{name:state.name,iduser:state.iduser}).then( res=>{console.log(res)});
    console.log(state)

  }

  return (
    <div onSubmit={ (e)=> submit(e)}>
      <form >
        <input
          onChange={  (e)=>handel(e) }
          id="name"
          value={state.name}
          placeholder="name"
          type="text"
        ></input>
        <input
          onChange={  (e)=>handel(e) }
          id="iduser"
          value={state.iduser}
          placeholder="iduser"
          type="text"
        ></input>
        <button>submit</button>
      </form>
    </div>

  );
}

Here is a util function modified (another post on stack) for get and post both. Make Util.js file.

let cachedData = null;
let cachedPostData = null;

const postServiceData = (url, params) => {
    console.log('cache status' + cachedPostData );
    if (cachedPostData === null) {
        console.log('post-data: requesting data');
        return fetch(url, {
            method: 'POST',
            headers: {
              'Accept': 'application/json',
              'Content-Type': 'application/json',
            },
            body: JSON.stringify(params)
          })
        .then(response => {
            cachedPostData = response.json();
            return cachedPostData;
        });
    } else {
        console.log('post-data: returning cachedPostData data');
        return Promise.resolve(cachedPostData);
    }
}

const getServiceData = (url) => {
    console.log('cache status' + cachedData );
    if (cachedData === null) {
        console.log('get-data: requesting data');
        return fetch(url, {})
        .then(response => {
            cachedData = response.json();
            return cachedData;
        });
    } else {
        console.log('get-data: returning cached data');
        return Promise.resolve(cachedData);
    }
};

export  { getServiceData, postServiceData };

Usage like below in another component

import { getServiceData, postServiceData } from './../Utils/Util';

constructor(props) {
    super(props)
    this.state = {
      datastore : []
    }
  }

componentDidMount = () => {  
    let posturl = 'yoururl'; 
    let getdataString = { name: "xys", date:"today"};  
    postServiceData(posturl, getdataString)
      .then(items => { 
        this.setState({ datastore: items }) 
      console.log(items);   
    });
  }

Here is the simple method to define and call post APIs in reactjs. Install axios using command npm install axios and call post req method wherever you want, it will return array that contains 100 elements.

// Define post_req() Method in authAction.js

import axios from 'axios';

const post_req = (data) => {
return new Promise((resolve, reject) => {
const url = 'https://jsonplaceholder.typicode.com/posts'
const header = {
    "Access-Control-Allow-Origin": "*",
    "Content-Type: application/json"
}
axios({
    method: 'post',
    url: url,
    data: data,
    headers: header
 });
 .then((res)=>{resolve(res);})
 .catch((err)=>{reject(err);})
 })
}

// Calling post_req() Method in react component 
import React, { Component } from 'react';
import { post_req } from 'path of file authAction.js'

class MyReactComponent extends Component {
constructor(props) {
super(props);
this.state = {
 myList:[]
 };
}
componentDidMount() {
let data = {
 .......
 } 
 this.props.post_req(data)
 .then((resp)=>{this.setState({myList:resp.data})})
 .catch((err)=>{console.log('here is my err',err)})
}
render() {
return (
  <div>
    ....
  </div)
 }
}
export default MyReactComponent;

Here is a quick example for v18+ while handling form data and creating a POST request with the data.

async function handleOrderSubmit(event){
  event.preventDefault()

  try{
    const formData= {name: event.target.name.value, email: event.target.email.value, message: event.target.name.message}
    const requestOptions = {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(formData)
    };
    const response = await fetch('https://www.example.com/form', requestOptions);
    const data = await response.json();
    navigate("/form-response", { state: {data: data, status: true} })
  }
  catch(error){
    navigate("/form-response", { state: {status: false} })
  }
}

Note 1: Using status on '/form-response' page, you can customise what to show user. For true, you can show a different section and for false a different one.

Note 2: If the status is successful, you can access data on the next page also and customise it according to user information.

Note 3: event.preventDefault() is important to avoid page reloading.