title: Javascript: What is function with two parenthesis brackets ()()?
body: <p>I recall somewhere seeing a function with two parenthesis brackets ()() like:</p>
  
  <pre><code>function add_numbers(number1)(number2)
  </code></pre>
  
  <p>What do you call such a function and what’s its usage? </p>
  
  <p>Thank you in advance and will be sure to vote up/accept answer</p>