How to lowercase or uppercase all array values in JavaScript

Today, we’ll explain to you how to lowercase or uppercase all array values in JavaScript. We have several ways to convert the values but in this short article, we will talk about the two different ways.

Ways to convert all array values to LowerCase or UpperCase

1. Using array map() method
2. Using for loop

1. Using array map() method

Using array map() method, we can iterate over all elements of the array and convert the case of the element as we want.

Let’s take an example for better understanding.

Convert an array values to LowerCase

Here, we will use the string method toLowerCase() along with an array map() method to convert the all array values into the LowerCase.

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = names.map(name => name.toLowerCase());

console.log(convertedNames);
// Output: ["john", "william", "elijah", "michael"]

Convert an array values to UpperCase

The same way to convert the array values into UpperCase using the toUpperCase() method.

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = names.map(name => name.toUpperCase());

console.log(convertedNames);
// Output: ["JOHN", "WILLIAM", "ELIJAH", "MICHAEL"]

2. Using for loop

Let’s do the same task using the for loop.

Convert an array values to LowerCase

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = [];
for (let i = 0; i < names.length; i++) {
  convertedNames[i] = names[i].toLowerCase();
}

console.log(convertedNames);
// Output: ["john", "william", "elijah", "michael"]

Convert an array values to UpperCase

let names = ["John", "William", "Elijah", "Michael"];

let convertedNames = [];
for (let i = 0; i < names.length; i++) {
  convertedNames[i] = names[i].toUpperCase();
}

console.log(convertedNames);
// Output: ["JOHN", "WILLIAM", "ELIJAH", "MICHAEL"]

You can also use the below simple way if you have a large array of values.

let convertedNames = names.join('$$').toLowerCase().split('$$');

let convertedNames = names.join('$$').toUpperCase().split('$$');

I hope you find this article helpful.
Thank you for reading. Happy Coding..!!