Async-Await

Asynchronous

function helloWorld() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve("Hello World!");
    }, 2000);
  });
}

const msg = async function () {
  //Async Function Expression
  const msg = await helloWorld();
  console.log("Message:", msg);
};

const msg1 = async () => {
  //Async Arrow Function
  const msg = await helloWorld();
  console.log("Message:", msg);
};

msg(); // Message: Hello World! <-- after 2 seconds
msg1(); // Message: Hello World! <-- after 2 seconds

Resolving Promises

let pro1 = Promise.resolve(5);
let pro2 = 44;
let pro3 = new Promise(function (resolve, reject) {
  setTimeout(resolve, 100, "foo");
});

Promise.all([pro1, pro2, pro3]).then(function (values) {
  console.log(values);
});
// expected => Array [5, 44, "foo"]

Async Await Promises

function helloWorld() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve("Hello World!");
    }, 2000);
  });
}

async function msg() {
  const msg = await helloWorld();
  console.log("Message:", msg);
}

msg(); // Message: Hello World! <-- after 2 seconds

Error Handling

let json = '{ "age": 30 }'; // incomplete data

try {
  let user = JSON.parse(json); // <-- no errors
  console.log(user.name); // no name!
} catch (e) {
  console.error("Invalid JSON data!");
}

Async await operator

function helloWorld() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve("Hello World!");
    }, 2000);
  });
}

async function msg() {
  const msg = await helloWorld();
  console.log("Message:", msg);
}

msg(); // Message: Hello World! <-- after 2 seconds

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