JavaScript Promises

JavascriptWeb DevelopmentObject Oriented Programming

Promises in JavaScript allow us to do asynchronous operations where the value is not known in advanced when the promise was being created. A promise can have three states pending, fulfilled and rejected.

Following is the code for promises in JavaScript −

Example

 Live Demo

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .sample {
      font-size: 18px;
      font-weight: 500;
      color: red;
   }
</style>
</head>
<body>
<h1>JavaScript Promises</h1>
<div class="sample"></div>
<button class="Btn">CLICK HERE</button>
<h3>
Click on the above button to display username using promises
</h3>
<script>
   let sampleEle = document.querySelector(".sample");
   document.querySelector(".Btn").addEventListener("click", () => {
      fetch("https://jsonplaceholder.typicode.com/users")
      .then((response) => response.json())
      .then((result) => {
         result.forEach((element) => {
            sampleEle.innerHTML += element.username + "<br>";
         });
      })
      .catch((err) => alert(err));
   });
</script>
</body>
</html>

Output

On clicking the ‘CLICK HERE’ button −

raja
Published on 11-May-2020 14:11:30
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