async function meaning code example

Example 1: async await

const data = async ()  => {
  const got = await fetch('https://jsonplaceholder.typicode.com/todos/1');
  
  console.log(await got.json())
}

data();

Example 2: how to make an async function

function resolveAfter2Seconds() {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve('resolved');
    }, 2000);
  });
}

//async function:
async function asyncCall() {
  console.log('calling');
  const result = await resolveAfter2Seconds();
  console.log(result);
  // expected output: 'resolved'
}

asyncCall();

Example 3: js async await

/* Notes:
	1. written like synchronous code
    2. compatible with try/catch blocks
    3. avoids chaining .then statements
    4. async functions always return a promise
    5. function pauses on each await expression
    6. A non promise value is converted to 
       Promise.resolve(value) and then resolved
*/

// Syntax
// Function Declaration
async function myFunction(){
  await ... // some code goes here
}
  
// Arrow Declaration
const myFunction2 = async () => {
  await ... // some code goes here
}
  
 // OBJECT METHODS

const obj = {
	async getName() {
		return fetch('https://www.example.com');
	}
}

// IN A CLASS

class Obj {
	// getters and setter CANNOT be async
	async getResource {
		return fetch('https://www.example.com');
	}
}

Example 4: async await

// ASYNC will always returns promises
// NOTE : AWAIT should be kept only inside ASYNC function
// AWAIT can't be used in regular function
/* TIPS : Js is single threaded & synchronous in nature BUT, we can
          make it as asyncronous by using (ASYNC/AWAIT)*/

//(Example 1 : fetching Random Image)
async function RandomImage(){  //remember async and await is powerful for async operations, always await should be inside of async only.

  try {
    const raw_response = await fetch("https://www.themealdb.com/api/json/v1/1/random.php");
      if (!raw_response.ok) { // check for the 404 errors
          throw new Error(raw_response.status);
      }
    const json_data = await raw_response.json();  //AWAIT
    let data = json_data.meals[0];

    console.log(data);
  }
  catch (error) { // catch block for network errors
      console.log(error); 
  }
}
RandomImage();


//(Example 2 : returning another promise)
console.log("1 is working");
console.log("2 is working");
  var AsyncFunction = async() => {
    var x = new Promise((resolve,reject) => {
        setTimeout(() => resolve("3 is working"), 3000);
    });
    var result = await x;
    return result;
  }
AsyncFunction().then(resolved => console.log(resolved));
console.log("3 is working");

Example 5: async

function resolveAfter2Seconds() {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve('resolved');
    }, 2000);
  });
}

async function asyncCall() {
  console.log('calling');
  const result = await resolveAfter2Seconds();
  console.log(result);
  // expected output: 'resolved'
}

asyncCall();

Example 6: async await

async function () {
  const fetchAPI = fetch(`https://bn-hadith-api.herokuapp.com/hadiths/0`);
  const response = await fetchAPI;
  const data = await response.json();
  console.log(data);
}