Gaafar

const makeRequest = () => {
  return promise1()
    .then(value1 => {
      // do something
      return Promise.all([value1, promise2(value1)])
    })
    .then(([value1, value2]) => {
      // do something          
      return promise3(value1, value2)
    })

Gaafar

const makeRequest = async () => {
  const value1 = await promise1()
  const value2 = await promise2(value1)
  return promise3(value1, value2)
}

Gaafar

const makeRequest = () => {
  return callAPromise()
    .then(() => callAPromise())
    .then(() => callAPromise())
    .then(() => callAPromise())
    .then(() => callAPromise())
    .then(() => {
      throw new Error("oops");
    })
}

Gaafar

const makeRequest = async () => {
  await callAPromise()
  await callAPromise()
  await callAPromise()
  await callAPromise()
  await callAPromise()
  throw new Error("oops");
}

makeRequest()

Gaafar

// this will not work in top level
// await makeRequest()

// this will work
makeRequest().then((result) => {
  // do something
})

Gaafar

Motivation

Easy access for a property in higher order functions, enables composition & piping

Examples

const strings = ["", "a"]
const filteredStrings = strings.filter(.length) // ["a"]

Gaafar

# cron tab
# 0 0 */5 * * /root/certbot-renew

#!/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
#old /root/certbot-auto renew
certbot renew

# don't forget chmod +x /root/certbot-renew

Gaafar

#!/bin/bash

# install:
# copy this file to /usr/local/bin/shove
# sudo chmod +x /usr/local/bin/shove
# then use: shove alpha

remoteBranch=${1?Please specify origin branch to shove}
localBranch=`git symbolic-ref --short -q HEAD`
read -p "Force push local branch ($localBranch) => (origin/$remoteBranch). Proceed? (y/n) " -r

Gaafar

const getJSON = () => {
  // here url is not defined and will throw an error
  // since the error is thrown before returning the promise,
  // it won't be caught by .catch
  console.log(url)
  
  return Promise.resolve()
}

const makeRequest = () => getJSON()

Gaafar

// version 1: using promise with utility functions
const passthrough = fn => data => Promise.all([data, fn(data)])
const spread = fn => list => fn(...list)

const makeRequest = () => promise1()
  .then(passthrough(promise2))
  .then(spread(promise3))
  

// version 2: async/await