title: requireNotNull alternative in TypeScript for null safety
body: <p>I recently started learning Kotlin and was wondering if TypeScript has a <code>requireNotNull</code> similar check or method?</p>
  <p>I'm using a function getUserId() which either return a string or null.</p>
  <pre><code>const userId = getUserId()
  
  MakeNetworkFetch(userId) // could be nulll
  
  // Also at the moment I'm using this below code, which makes Typescript linter happy
  
  MakeNetworkFetch(userId!!)
  
  </code></pre>
  <p>I tried searching for Double-bang after variable but could not find anything</p>