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toLowerCase() in JavaScript – How to Convert String to Lowercase

Whenever you use toLowerCase() on a string, the method does the following:

  1. It converts its calling string to lowercase.
  2. It returns the new version of the calling string—without changing the original string.
note
  • A calling string is a string on which you used toLowerCase(). So, in "Hello, World!".toLowerCase(), "Hello, World!" is the calling string.
  • toLowerCase() is sometimes written as String.prototype.toLowerCase() because it is a method of the String object's prototype property.

Syntax of the toLowerCase() Method​

toLowerCase() does not accept any argument. Here is the syntax:

callingString.toLowerCase();

Example 1: Convert CodeSweetly to Lowercase​

"CodeSweetly".toLowerCase();

// The invocation above will return: "codesweetly"

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Example 2: Convert a JavaScript String to Lowercase​

"FRIDAY, MY FRIEND, WAS BORN ON FRIDAY".toLowerCase();

// The invocation above will return: "friday, my friend, was born on friday"

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tip

To convert a string to uppercase, use toUpperCase().

Overview​

String toLowerCase() method's tidbit

Use the toLowerCase() method to convert your string to lowercase.

toLowerCase() returns the lowercase version of its calling string.