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How to wrap setTimeout() method in a promise ?

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To wrap setTimeout in a promise returned by a future. We can wrap setTimeout in a promise by using the then() method to return a Promise. The then() method takes up to two arguments that are callback functions for the success and failure conditions of the Promise. This function returns a promise. There can be two different values if the function called onFulfilled that’s mean the promise is fulfilled. If the function onRejected is called that means the promise is rejected. 

Syntax:

Promise.then(onFulfilled, onRejected)

The below example will illustrate the approach: 

Example 1: In this example, we will see the use of Promise with then() block and setTimeout() method.

HTML

<!DOCTYPE html>
<html>
  
<head>
    <title>
        How to wrap setTimeout in a promise?
    </title>
</head>
  
<body>
    <h1 style="color:green;">
        GeeksforGeeks
    </h1>
  
    <h3>
        How to wrap setTimeout in a promise?
    </h3>
    <br>
  
    <button onclick="change()">
        Click to print
    </button>
    <p id="gfg"></p>
    <script>
        function change() {
            return new Promise(function (resolve, reject) {
          
                // Setting 2000 ms time
                setTimeout(resolve, 2000);
            }).then(function () {
                document.getElementById("gfg").innerHTML = 
                "Wrapped setTimeout after 2000ms";
            });
        }
    </script>
  
</body>
  
</html>

                    

Output:

How to wrap setTimeout() method in a promise ?

How to wrap the setTimeout() method in a promise?

Example 2: In this example, we will see the use of Promises with the async function and setTimeOut() method.

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" 
          content="IE=edge">
    <meta name="viewport" 
          content="width=device-width, 
                   initial-scale=1.0">
</head>
<body>
    <h1 style="color:green;">
        GeeksforGeeks
    </h1>
      
    <h3>
        How to wrap setTimeout in a promise?
    </h3>
    <br>
      
    <button onclick="resolvePromise()">
        Click to print
    </button>
    <p id="gfg"></p>
    <script>
        let gfg = document.getElementById('gfg');
  
        // function for promise example
        async function resolvePromise() {
            let newPromise = 
                new Promise(function (resolve, reject) {
                setTimeout(function () {
                    resolve("Hello Geeks. Wrapped 
                             setTimeout() in a promise");
                }, 1000);
            });
            let result = await newPromise;
            gfg.innerHTML = result;
        }
    </script>
</body>
</html>

                    

Output:

 

Reference: Promise.prototype.then() Method



Last Updated : 16 May, 2023
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