---
title: Javascript Async/Await
description: "*“async and await make promises easier to write”* **async** makes a function return a Promise **await** makes a function wait for a Promise ## Async Syntax The keyword `async` before a function makes the function return a promise: ### Example `async function myFunction() {…"
url: "https://apprentice.mn/docs/javascript-async-await/"
updated: "2021-05-19"
category: Javascript
---

# Javascript Async/Await

*“async and await make promises easier to write”*

**async** makes a function return a Promise

**await** makes a function wait for a Promise

## Async Syntax

The keyword `async` before a function makes the function return a promise:

### Example

      `async function myFunction() {
  return "Hello";
}`

Is the same as:

       `async function myFunction() {
  return Promise.resolve("Hello");
}`

Here is how to use the Promise:

       `myFunction().then(
  function(value) { /* code if successful */ },
  function(error) { /* code if some error */ }
);`

### Example

     `async function myFunction() {
  return "Hello";
}
myFunction().then(
  function(value) {myDisplayer(value);},
  function(error) {myDisplayer(error);}
);`

Or simpler, since you expect a normal value (a normal response, not an error):

### Example

      `async function myFunction() {
  return "Hello";
}
myFunction().then(
  function(value) {myDisplayer(value);}
);`

## Await Syntax

The keyword `await` before a function makes the function wait for a promise:

       `let value = await promise;`

The `await` keyword can only be used inside an `async` function.

---

## Example

Let’s go slowly and learn how to use it.

### Basic Syntax

      `async function myDisplay() {
  let myPromise = new Promise(function(myResolve, myReject) {
    myResolve("I love You !!");
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();`

### Waiting for a Timeout

     `async function myDisplay() {
  let myPromise = new Promise(function(myResolve, myReject) {
    setTimeout(function() { myResolve("I love You !!"); }, 3000);
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();`

### Waiting for a File

     `async function getFile() {
  let myPromise = new Promise(function(myResolve, myReject) {
    let req = new XMLHttpRequest();
    req.open('GET', "mycar.html");
    req.onload = function() {
      if (req.status == 200) {myResolve(req.response);}
      else {myResolve("File not Found");}
    };
    req.send();
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

getFile();`

## Browser Support

ECMAScript 2017 introduced the JavaScript keywords `async` and `await`.

The following table defines the first browser version with full support for both:

| ![](https://www.w3schools.com/images/compatible_chrome.gif) | ![](https://www.w3schools.com/images/compatible_edge.gif) | ![](https://www.w3schools.com/images/compatible_firefox.gif) | ![](https://www.w3schools.com/images/compatible_safari.gif) | ![](https://www.w3schools.com/images/compatible_opera.gif) |
| --- | --- | --- | --- | --- |
| Chrome 55 | Edge 15 | Firefox 52 | Safari 11 | Opera 42 |
| Dec, 2016 | Apr, 2017 | Mar, 2017 | Sep, 2017 | Dec, 2016 |

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