title: Why assigning 'null' to a variable before using it, sometimes
body: <p>Taking the following code snippet as an example:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>//variable a,b and c will hold Constructors later
  var a = null;
  var b = null;
  var c;
  
  function setup() {
    //assign those Constructors to variable a,b and c
    a = new ControlsAndInput();
    b = new p5.FFT();
    c = new myOwnConstructor();
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>I noticed some people like to declare and assign the <code>null</code> value to a global variable which will be used later. </p>
  
  <p><strong>The question is:</strong> what's the differences between assigning a <code>null</code> value and not assigning a <code>null</code> value to a variable before using it? Is there any difference between var <code>a</code>,<code>b</code> and <code>c</code> in above example, such that unlike <code>a</code> and <code>b</code>, <code>c</code> was not assigned a <code>null</code> value at the start, could this cause any potential bug, why I need to assign <code>null</code> to a variable before using it sometimes</p>