async and await

async function test() {
//Invoking an async function returns a promise.
const promise1 = test2();
console.log(promise1);

const output = await promise1.catch((error) => console.log(error));
console.log("Output = " + output);

const promise2 = test3();
console.log(promise2);

const output2 = await promise2.catch((error) => console.log(error));
console.log("Output = " + output2);

//The following commented code is incorrect as the function test3 doesn't return a promise and also not an async
//function.
//The await operator is used to wait for a Promise. It can only be used inside an async function.
//If the value is not a Promise, it converts the value to a resolved Promise, and waits for it.
//const output3 = await test4().catch((error) => console.log(error));
const output3 = await test4();
console.log("Output = " + output3);

const promise3 = test5();
console.log(promise3);

const output4 = await promise3;
console.log("Output = " + output4);
}

async function test2() {
return new Promise((resolve, reject) => {
    setTimeout(function(){
      resolve(100);
    }, 5000);
  });
}

async function test3() {
// throw Error("Testing Errors.");
return 200;
}

function test4() {
return 300;
}

function test5() {
return new Promise((resolve, reject) => {
    setTimeout(function(){
      resolve(400);
    }, 5000);
  });
}

test();

--------------------------------------------------------------
Output:

Promise { <pending> }

//after 5 seconds

Output = 100
Promise { 200 }
Output = 200
Output = 300
Promise { <pending> }

// after 5 seconds

Output = 400