Mutations - trying to understand ( .toLowerCase() )

When I try to convert the entire argument to lower case, it doesn’t seem to convert?

Your code so far

function mutation(arr1) {


let fun = arr1.toLowerCase();


mutation(["heLLo", "hEy"]);

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User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36.

Link to the challenge:

toLowerCase is a string method so only works on strings. arr1 is an array, not a string. You are trying to apply it to an array.

arr1 is an array of strings though. Try applying it to each element individually.