Can a method be used on a function?

The terminal gave me a type error that the method I was using (.toUpperCase) on a function is incorrect. So are methods not meant to be used on functions?

You haven’t linked to the exercise/challenge. But based on the parameter name arr, I assume that the expected argument is supposed to be an array of strings.

The toUpperCase method can be used with a string, but you can’t apply the toUpperCase method directly on an array. You must iterate over the array and call the toUpperCase method on each string.

In your screenshot,

// Your function:
function shoutGreetings(arr) {
    console.log(arr.toUpperCase() + '!')

let word = "hello";
let myArray = ["hello", "there"];

// Output: "HELLO!"

// TypeError

To add onto that, if you wanted to upper case every word in an array, as mtrtmk mentioned, you’d have to loop through it somehow. You could either create a standard for loop, or use something like .map() or .forEach() - i.e…

function shoutGreetings(arr) {
    arr.forEach(greeting => console.log(greeting.toUpperCase() + "!")

const greetingsArray ['hello', 'bonjour', 'hoi']
// logs 'HELLO', 'BONJOUR', and 'HOI'

This will perform the desired function of logging to the console every item in the array provided with the transformation of the .toUpperCase() method.

1 Like

Thank you, now I understand it.