JavaScript String toLowerCase() Method

Last Updated : 16 Jan, 2026

The JavaScript toLowerCase() method Converts all characters of a string to lowercase and returns a new string without changing the original.

  • Used for case-insensitive comparisons
  • Helps standardize user input
  • Common in text formatting and data validation
  • Does not modify the original string
JavaScript 
let text = "HeLLo WoRLd";

let result = text.toLowerCase();

console.log(result);

Syntax:

str.toLowerCase();

Return value:

The toLowerCase() method returns a modified version of the original string. It converts all uppercase letters into lowercase.

  • Returns a new string.
  • All uppercase letters are converted to lowercase.
  • The original string is not changed.

[Example 1]: Converting all characters of a string to lowercase

The toLowerCase() method converts all characters in the string 'GEEKSFORGEEKS' to lowercase. The resulting string 'geeksforgeeks' is then logged to the console.

JavaScript 
let str = 'GEEKSFORGEEKS';

// Convert to lowercase
let string = str.toLowerCase();
console.log(string);

[Example 2]: Converting elements of array to lowercase

The code uses map() to convert each array element to lowercase with toLowerCase(), producing ['javascript', 'html', 'css'] and logging it to the console.

JavaScript 
let languages = ['JAVASCRIPT', 'HTML', 'CSS'];

let result = languages.map(lang => lang.toLowerCase());
console.log(result);
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