JavaScript String.toLowerCase() Method

The string.toLowerCase() method is used to change the uppercase letters of a string into lowercase while creating a new string. In JavaScript, toLowerCase() is used with other methods, including string.slice(), to change all the letters into lowercase except the first letter while creating a string.

Syntax of JavaScript string.toLowerCase():

refString.toLowerCase();
refString.slice(1).toLowerCase();

Parameter

This method does not take any parameters.

Return

It returns a new string after changing all the letters of a string to lowercase.

Example Codes: Use the string.toLowerCase() Method to Change the Uppercase Letters of a String to Lowercase

The string.toLowerCase() method converts all the letters of the given string into lowercase characters while creating a new string without changing the reference string in JavaScript.

In the example below, we have created a toggle case string. While using the toLowerCase() method to convert all the letters to lowercase of a given string, we have not passed any parameter.

var string = 'Select UpperCase or LowerCase Letters.';
let lwStr = string.toLowerCase();
console.log(lwStr);

Output:

select uppercase or lowercase letters.

Example Codes: Use the string.toLowerCase() Method to Convert the Entire String to Lowercase Except for the First Letter

Since the string.toLowerCase() method can convert all the letters of a string into lowercase characters, we can use the string.slice() method to exclude the first letter. In this example, we have got the first letter with string[0] and the remaining letters using string.slice().toLowerCase method.

let string = 'CAFÉ';
let upStr = string[0];
let lwstr = string.slice(1).toLowerCase();
console.log(upStr + lwstr);

Output:

Café

The string.toLowerCase() method converts the entire string to lowercase. To convert the only substring of the referencestring, users can use the string.slice() method with the toLowerCase() method in JavaScript.