title: What does colon mean in function definition in Javascript?
body: <p>I was thinking that colons can only work in object literals. 
  But when I ran the following code, browser didn't give me any error.
  And I also can't figure out what does the colon do in the function.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>var testFn = () =&gt; {
      abc: 1;
  }
  
  testFn();
  </code></pre>
  
  <p>Can you tell me what does this code do?</p>