title: Why would not the parent promise not catch the nested promise's rejection?
body: <p>Why would the nested rejected promise not be caught by the parent promise? But, If I do a "throw" inside the parent promise, it will get caught. </p>
  
  <pre><code>var parent = new Promise((res, rej) =&gt; {
      // this DOES NOT get caught by the parent. 
      Promise.reject("A plain reject");
  
      // this gets caught by the parent
      // throw new Error("Arbitrary  error");
  });
  
  parent.catch(err =&gt; {
      console.log("parent catches the error");
  });
  </code></pre>
  
  <p>Update: I'm not trying to rewrite this where the parent catches the rejected promise. I just want to understand the "why"? Thanks!</p>