sleep() in JavaScript

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms))
}

async function demo() {
  console.log('Taking a break...')
  await sleep(2000)
  console.log('Two seconds later, showing sleep in a loop...')

  // Sleep in loop
  for (let i = 0; i < 5; i++) {
    if (i === 3)
      await sleep(2000)
    console.log(i)
  }
}

demo()

This is it. await sleep(<duration>).

Or as a one-liner:

await new Promise(r => setTimeout(r, 2000))

Note

await can only be executed in functions prefixed with the async keyword, or at the top level of your script in some environments (e.g., the Chrome DevTools console, or Runkit).

await only pauses the current async function

Two new JavaScript features helped write this "sleep" function:

• Promises, a native feature of ES2015 (aka ES6). We also use arrow functions in the definition of the sleep function.
• The async/await feature lets the code explicitly wait for a promise to settle (resolve or reject).