Can I use "Typeof" to check if a function argument is an array? (stuck on code challenge)

Question

I am stuck on a code challenge, the task was to create a function which accepts an array and returns it's length but returns 0 if the argument (input) isn't an array. (a string, number, or undefined value)

I wrote:

function arrayCounter (myArray) {

return myArray.length

if (typeof myArray === 'string') { return 0; }

if (typeof myArray === 'undefined') { return 0 }

if (typeof myArray === 'number') return 0 }

}

i want to understand what I'm doing wrong, and whre my error in logic is.

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 (myArray) {
        return 0; 
        if (typeof myArray === 'array') {
          return myArray.length;
        }


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

Answer 1 · 2014-12-23T02:02:16Z

December 23, 2014 2:02am

First, you have a return statement as your first line. This will cause the function to return that value and exit out. The other lines of code will not be executed. The typeof used on an array object will return object not array, so probably not what you are looking for. I used Array.isArray(param) and it worked for me. You only have one test and not three.

  function arrayCounter(param) {
        if ( Array.isArray(param)) {
          return param.length;
        }else {
          return 0;
        }
      }

Hope this helps.

Answer 2 · 2014-12-23T02:25:39Z

December 23, 2014 2:25am

Hi Zach,

See the below link which shows a few different ways to approach this problem from a more intermediate level.

https://teamtreehouse.com/forum/stuck-on-stage-5-functions-quiz

Welcome to the Treehouse Community

Looking to learn something new?

Zach Saul

Zach Saul

Can I use "Typeof" to check if a function argument is an array? (stuck on code challenge)

2 Answers

Jeremy Faith

Jeremy Faith

Chris Shaw

Chris Shaw