JavaScript - Wait for an API Request to Return in JS

Last Updated : 29 Nov, 2024

For waiting of an API we must need to use express and nodejs to run the JavaScript code. we will create a simple Node.js-based API using Express that returns a JSON response. This will demonstrate how to make API calls using Async/Await in JavaScript.

Create a Simple Express API

First, install the required packages by running:

npm install express cors

Create a server.js file with the following code:

JavaScript

const express = require('express');
const cors = require('cors');

const app = express();
const PORT = 5000;

app.use(cors())

// API endpoint to return a simple message
app.get('/getData', (req, res) => {
  res.json({ message: "This is a response from the Express API" });
});
// Default Code when u start server 
app.get('/',(req,res)=>{
    res.send("hello from the server ");
})
// Start the server
app.listen(PORT, () => {
  console.log(`API is running at http://127.0.0.1:${PORT}`);
});

JavaScript Example Without Using Async/Await

Below is the code for calling the API without using Async/Await. This will demonstrate the default asynchronous behavior in JavaScript.

The fetchDataWithoutAsync function calls the API and immediately moves to the next line, logging 'Statement 2'.
Since the API call is asynchronous, console.log('Statement 2') is executed before the API response is received, demonstrating out-of-order execution.

JavaScript

function makeGetRequest(path) {
    axios.get(path).then(
        (response) => {
            var result = response.data;
            console.log('Processing Request');
            return (result);
        },
        (error) => {
            console.log(error);
        }
    );
}
function main() {
    let response = makeGetRequest('http://127.0.0.1:5000/test');
    console.log(response);
    console.log('Statement 2');
}
main();

Output:

JavaScript Example Using Async/Await

Now, let’s see how we can fix this issue by using Async/Await.

The async keyword ensures that fetchDataWithAsync is asynchronous.
The await keyword pauses the execution until the promise (API call) is resolved.
The program waits for the API response before logging 'Statement 2', ensuring the correct execution order.

JavaScript

function makeGetRequest(path) {
    return new Promise(function (resolve, reject) {
        axios.get(path).then(
            (response) => {
                var result = response.data;
                console.log('Processing Request');
                resolve(result);
            },
                (error) => {
                reject(error);
            }
        );
    });
}

async function main() {
    let result = await makeGetRequest('http://127.0.0.1:5000/test');
    console.log(result.result);
    console.log('Statement 2');
}
main();