title: sum function in Javascript
body: <p>When I create a simple Visual Studio project and add JavaScript and HTML items to it, I seem to have access to all built in functions, such as <code>indexOf()</code>, <code>search()</code>, <code>slice()</code>, <code>range()</code>, etc...</p>
  
  <p>However, when I try to use the <code>sum()</code> function (e.g. <code>console.log(sum(range(1, 10)));</code>) I get the following error message:</p>
  
  <blockquote>
    <p>Uncaught ReferenceError: sum is not defined</p>
  </blockquote>
  
  <p>Putting this message within double quotes and adding the JavaScript keyword in Google did not bring up a webpage that tells me what I am missing, hence this basic question here.</p>
  
  <p>Am I missing something like a library that <code>sum</code> is included in? What am I doing wrong that only this particular function is not recognized?</p>