test.js

function timedLog(value, ms) {
  return new Promise((resolve, reject) => {
     setTimeout(() => {
        console.log(value)
        resolve()
     }, ms)
  })
}

async function doSomething() {
  let arr = [300, 200, 100]

  for (let i of arr) {
    await timedLog(i, i)
  }
}

doSomething()