In an earlier article, we looked at different ways to capitalize the first letter of a string to uppercase in JavaScript.
In this article, you'll learn how to uppercase or lowercase a string using JavaScript.
JavaScript provides two built-in functions for converting strings to uppercase and lowercase. Let us look at them.
toUpperCase() Method
The toUpperCase() method transforms a string into uppercase letters in JavaScript. It doesn't change the original string and returns a new string equivalent to the string converted to uppercase.
Here is an example:
const str = 'JavaScript World!'
// convert string to uppercase
const upperStr = str.toUpperCase()
// print the new string
console.log(upperStr)
// output: JAVASCRIPT WORLD!
toLowerCase() Method
The toLowerCase() method does the opposite of the toUpperCase() method. It converts all characters of the string to lowercase:
const str = 'JavaScript World!'
// convert string to lowercase
const lowerStr = str.toLowerCase()
// print the new string
console.log(lowerStr)
// output: javascript world!
Both these methods work in all modern browsers and are supported back to at least Internet Explorer 6.
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