title: How to run an array of promises in sequence
body: <p>I need to run some promises on an array of items but I don't know the length of the array. How do I run these promises in sequence? This is how I do it asynchronously:</p>
  
  <pre><code>const arrayABC = [a, b, c.....x, y, z] // length unknown
  const promises = arrayABC.map(function(item) {
     doSomething(item)
     }
  return Promise.all(promises)
  </code></pre>
  
  <p>I need the promises to run through them one by one.</p>