title: how axios promise define errors
body: <p>I have some questions regarding promise and axios.</p>
  
  <p>In the below axios example, I am wondering how is it defined to run the catch code.</p>
  
  <p>Is it based on response http status code? like 400?</p>
  
  <pre><code>axios.get('/user?ID=12345')
    .then(function (response) {
      console.log(response);
    })
    .catch(function (response) {
      console.log(response);
    });
  </code></pre>
  
  <p>Thanks.</p>