JavaScript/async.html at master · vishal-vaish/JavaScript · GitHub

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<!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">
    <title>Document</title>
</head>
<body>

</body>
</html>
<script>
    // function foo(){
    //     return new Promise(function(resolve,reject){
    //         resolve("Some Data");
    //     })
    // }

    //This whole foo function we can write as
    function creatOrder(){
        return new Promise((resolve, reject)=>{
            setTimeout(()=>{
                resolve("Order created");
            },2000);
        })
    }

    function proceedToPayment(){
        return new Promise((resolve, reject)=>{
            setTimeout(()=>{
                // resolve("Order created");
                reject("Order created");
            },2000);
        })
    }

    async function foo(){
        //when you add async keyword in front of regular function
        //It automatically return a promise from that function
        try{
        const orderId=await creatOrder();
        //pauses the Execution and waits for the promise to resolve or reject
        //After the promise is resolved the function execution continue from the point where it left
        await proceedToPayment();
        console.log("Last Statement of Async Function");
        }
        catch(err){
            console.log("Error in",err);
        }
    }

    //1. await can only be use inside a async function
    //Await keyword makes the function pause the execution and wait for the promise to resolve
    foo();
    console.log(3);
    console.log(4);
</script>