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JavaScript

Posted by Gregory Ledger
Gregory Ledger
6,116 Points

Why does .toString() method return undefined?

Trying out some code in console.

<script>
var fruits = ["Banana", "Orange", "Apple", "Mango"];
var newFruits = fruits.toString();
document.getElementById("demo").innerHTML = newFruits;
</script>

in the console I type in:

typeof newFruits; //returns "undefined"

My thought is that fruits.toString() would have stored the string in newFruits, so the type should be a string. Why does it return "undefined"

Alexander Acker
Alexander Acker
18,123 Points

Believe that .toString() should only be utilized when you want to convert a number into a string. If you're looking to make your array fruits into a full string that you'd like to apply to the #demo element, recommend using the .join() method and applying a (" ") within the join parameter. Such like,

<script>
var newFruits = fruits.join(" ");
document.getElementById("demo").innerHTML = newFruits;
</script>
Michael Liendo
Michael Liendo
15,326 Points

Alexander Acker https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toString

3 Answers

Michael Liendo
Michael Liendo
15,326 Points
Michael Liendo
Michael Liendo
15,326 Points

I suspect a typo? Write all the JS in the console to check the value. Your code is fine and I was able to test to make sure.

Alexander Acker
Alexander Acker
18,123 Points
Alexander Acker
Alexander Acker
18,123 Points

Boom thanks Michael! Learn something new each day :)

Gregory Ledger
Gregory Ledger
6,116 Points

Thanks, I would normally use join. But I'm trying to learn array methods, and .toString() is an array method according to Mozilla Developer Network. arr.toString() is supposed to return a string but I'm getting undefined.

Steven Parker
Steven Parker
243,318 Points
Steven Parker
Steven Parker
243,318 Points

Are you still getting undefined?

I agree with Michael, you probably had a typo. Your code works for me.

You might try this variant, which also worked for me:

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var newFruits = fruits.toString();
console.log("newFruits has type '" + typeof newFruits + "', and contains: " + newFruits);