Cant figure out how to check for undefined.

Question

I have this code which is appended but it doesnt work. I cant figure out what the mistake is.

The message on top is that I am not checking for undefined.

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>JavaScript Foundations: Functions</title>
    <style>
      html {
        background: #FAFAFA;
        font-family: sans-serif;
      }
    </style>
  </head>
  <body>
    <h1>JavaScript Foundations</h1>
    <h2>Functions: Return Values</h2>
    <script>

      function arrayCounter (a){
        if (a.isArray)
        {
        return a.length;
        }
      else if(typeof a==='string')
      {
      return 0;
      }
        else if(typeof a==='number')
        {
        return 0;
        }
        else if(typeof a==="undefined")
        {
        return 0;
        }
      }


    </script>
  </body>
</html>

Answer 1 · 2014-12-16T21:43:49Z

December 16, 2014 9:43pm

I think the if(a.isArray) is not working as it should

here is the code that works

  function arrayCounter (a){
    if (a instanceof Array)
    {
    return a.length;
    }
  else  
  {
  return 0;
  } 
  }

Answer 2 · 2014-12-16T21:37:06Z

December 16, 2014 9:37pm

It should work if you remove the quotation marks around undefined.

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raj kanwar

raj kanwar

Cant figure out how to check for undefined.

2 Answers

haunguyen

haunguyen

Michael Escoto

Michael Escoto