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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 48,850 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,850 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 48,850 Points
Clayton Perszyk
Clayton Perszyk
Treehouse Moderator 48,850 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>