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JavaScript JavaScript Foundations Functions Return Values

Michael Baker
Michael Baker
7,731 Points
Posted by Michael Baker
Michael Baker
7,731 Points

how do you pass an array as a parameter in a function?

Here's as far as I got:

  function arrayCounter (array) {
    if (typeof array === 'undefined', 'string', 'number'){
        return 0;
    }
      return array.length;
  }

what am I doing wrong here...?

4 Answers

Dave McFarland
STAFF
Dave McFarland
Treehouse Teacher
Dave McFarland
Dave McFarland
Treehouse Teacher

Your conditional statement isn't correct. You can't use commas like that. You'd need to create three tests using the || operator like this:

if (typeof array === "undefined" || typeof array === "string" || typeof array === "number" )

However, even that won't correctly test for an Array. You're better off using JavaScript's instanceof operator. It can tell you if a variable is an array or not like this:

function arrayCounter (array) {
    if (array instanceof Array) {
        return array.length;
    } else {
        return 0;
}
var myArray = [1,2,3];
console.log(arrayCounter(myArray)); // prints 3 to the console
var myString = 'test';
console.log(arrayCounter(myString)); // prints 0 to the console
Michael Baker
Michael Baker
7,731 Points
Michael Baker
Michael Baker
7,731 Points

Thanks Dave, That was a tricky one - I assumed I was being asked how to test for those 3 instances (string, undefined or number). Making a catch-all is much cleaner. Michael

Michael Baker
Michael Baker
7,731 Points
Michael Baker
Michael Baker
7,731 Points

Thanks Dave, That was a tricky one - I assumed I was being asked how to test for those 3 instances (string, undefined or number). Making a catch-all is much cleaner. Michael

Dave McFarland
STAFF
Dave McFarland
Treehouse Teacher
Dave McFarland
Dave McFarland
Treehouse Teacher

Michael, I think my solution works better than testing for 'string', 'undefined' and 'number', because in JavaScript there are other types as well, such as boolean, function and object. What's even trickier is that if you use typeof with an array you don't get 'array' as the result; you get 'object'. 

console.log(typeof [1,2,3]); // prints 'object' NOT 'array'

However, since this is part of a code challenge, my answer may not work. I think the code challenge is looking for the use of the typeof operator like this:

var arrayCounter = function(array) {
        if (typeof array === 'string' ||  typeof array === 'number' || typeof array === 'undefined') {
          return 0;
        } else {
          return array.length;
        }
      }