Promise

const condition = true;
 
const promise = new Promise((resolve, reject) => {
  if (condition)
    resolve('Valid promise');
  else
    reject('Invalid promise');
});
 
promise.then(r => console.log(r));
//=> Valid promise

const condition = true;
 
const promise = new Promise((resolve, reject) => {
  if (condition)
    resolve('Valid promise');
  else
    reject('Invalid promise');
});
 
promise.then(r => console.log(r));
//=> Valid promise

const condition = false;
 
const promise = new Promise((resolve, reject) => {
  if (condition)
    resolve('Valid promise');
  else
    reject('Invalid promise');
});
 
promise.then(r => console.log(r)).catch(r => console.log(r));
//=> Invalid promise

const condition = false;
 
const promise = new Promise((resolve, reject) => {
  if (condition)
    resolve('Valid promise');
  else
    reject('Invalid promise');
});
 
promise.then(r => console.log(r)).catch(r => console.log(r));
//=> Invalid promise

function sum(a, b) {
  return a + b;
}
 
function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
console.log(sum(1, 1));
console.log(sumPromise(2, 2));
sumPromise(2, 2)
  .then((res) => console.log(res))
  .catch((err) => console.log(err));
console.log(sum(3, 3));
 
//=>
// 2
// Promise { <pending> }
// 6
// 4

function sum(a, b) {
  return a + b;
}
 
function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
console.log(sum(1, 1));
console.log(sumPromise(2, 2));
sumPromise(2, 2)
  .then((res) => console.log(res))
  .catch((err) => console.log(err));
console.log(sum(3, 3));
 
//=>
// 2
// Promise { <pending> }
// 6
// 4

function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
sumPromise(2, 2)
  .then((res) => sumPromise(res, 2))
  .then((res) => console.log(res))
  .catch((err) => console.log(err)); //=> 6

function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
sumPromise(2, 2)
  .then((res) => sumPromise(res, 2))
  .then((res) => console.log(res))
  .catch((err) => console.log(err)); //=> 6

function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
async function sumAsync(a, b) {
  const sleep = (m) => new Promise(r => setTimeout(r, m))
 
  if (isNaN(a) || isNaN(b)) {
    throw new Error('Invalid numbers');
  } else {
    await sleep(200);
    return a + b;
  }
}
 
async function result() {
  try {
    const res = await sumPromise(2, 2);
    return await sumAsync(2, res);
  } catch (error) {
    if (error instanceof Error) {
      console.log(error.message);
    } else {
      console.log(err);
    }
  }
}
 
result().then((res) => console.log(res)); //=> 6

function sumPromise(a, b) {
  const promise = new Promise((resolve, reject) => {
    if (isNaN(a) || isNaN(b))
      reject('Invalid numbers');
    else
      setTimeout(() => resolve(a + b), 200);
  });
 
  return promise
}
 
async function sumAsync(a, b) {
  const sleep = (m) => new Promise(r => setTimeout(r, m))
 
  if (isNaN(a) || isNaN(b)) {
    throw new Error('Invalid numbers');
  } else {
    await sleep(200);
    return a + b;
  }
}
 
async function result() {
  try {
    const res = await sumPromise(2, 2);
    return await sumAsync(2, res);
  } catch (error) {
    if (error instanceof Error) {
      console.log(error.message);
    } else {
      console.log(err);
    }
  }
}
 
result().then((res) => console.log(res)); //=> 6