Promise <-> Async await equivalence

equivalence.js

"use strict"
// The following are equivalent (functionally)

// Async await
async function simple() {
  await setTimeout(() => console.log("hello, world!"), 1000);
}

// Promises
function simple_promise() {
  return Promise.resolve(() => setTimeout(() => console.log("hello, world!"), 1000));
}

// Async await
async function await_at_end() {
  let x = doSomethingAsync(); // x is a promise
  x = x.then(() => console.log("hello, world!"));
  await x;
}

// Promises
function await_at_end_promise() {
  let x = doSomethingAsync(); // x is a promise
  x = x.then(() => console.log("hello, world!"));
  return x;
}


// Async await
async function try_catch() {
  let result = -1;
  try {
    let x = await doSomethingAsync(); // x is a number
    result = x+1;
  } catch (err) {
    console.log(err.message);
  }
  return result;
}

// Promises
function try_catch_promise() {
  let result = -1;
  return doSomethingAsync()
    .then(x => result = x+1)
    .catch(err => console.log(err.message))
    .then(() => result);
}

// Async await
async function nested_catch() {
  try {
    await doSomethingAsync();
    try {
      await doThing2Async();
      console.log("done");
    } catch (err) {
      console.err(`thing2 failed with message ${err.message}`);
    }
  } catch (err) {
    console.err(`doSomething failed with message ${err.message}`);
  }
}

// Promises
function nested_catch_promise() {
  return doSomethingAsync()
    .then(() => {
      doThing2Async()
      .then(() => console.log("done"))
      .catch(err => console.err(`thing2 failed with message ${err.message}`))
    })
    .catch(err => console.err(`doSomething failed with message ${err.message}`))
}

// Async await
async function not_assigning() {
  let x = await 10;
  new Promise((resolve) => resolve(setTimeout(() => console.log(x), 100)));
  new Promise((resolve) => resolve(console.log(`Hello, ${x}`)));
  console.log("world!");
}

// Promises
function not_assigning_promise() {
  let x = Promise.resolve(10);
  x.then(n => setTimeout(() => console.log(n), 100));
  x.then(n => console.log(`Hello, ${n}, `));
  x = x.then(() => console.log("world!"));
  return x;
}