Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript JavaScript Foundations Functions Return Values

Posted by garitychapman
garitychapman
7,421 Points

How to check if value is an array Stage 5: Javascript Functions

On line 16 I need to build a function that takes an array as an argument. I then need to return 0 if the value passed in is a string number or undefined. I'm not sure how to do this. This is what I cam up with:

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 (array) {
        var array = [];
        if (typeof array != 'object') {
          return 0;
        }
        return array.length;
      } 


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

2 Answers

Clayton Perszyk
MOD
Clayton Perszyk
Treehouse Moderator 48,723 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,723 Points

hey garitychapman

Remove var array = []; from inside your function; it's overwriting the value that is being passed into your function. In other words the value that is passed in is being set to an empty array (hence return array.length will always equal zero).

clayton

Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,723 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,723 Points

Here's how I solved it: 

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

I used instanceof instead of typeof.

Devin Scheu
Devin Scheu
66,191 Points
Devin Scheu
Devin Scheu
66,191 Points

This should work for you, you dont need the var array=[]:

<!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 (array) {
        if (typeof array != 'object') {
          return 0;
        }
        return array.length;
      } 


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