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toUpperCase() in JavaScript – How to Convert String to Uppercase

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

  1. It converts its calling string to uppercase.
  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 toUpperCase(). So, in "Hello, World!".toUpperCase(), "Hello, World!" is the calling string.
  • toUpperCase() is sometimes written as String.prototype.toUpperCase() because it is a method of the String object's prototype property.

Syntax of the toUpperCase() Method​

Here is toUpperCase()'s syntax:

callingString.toUpperCase();

The snippet above shows that toUpperCase() does not accept any argument.

Example 1: Convert CodeSweetly to Uppercase​

"CodeSweetly".toUpperCase();

// The invocation above will return: "CODESWEETLY"

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Example 2: Convert a JavaScript String to Uppercase​

"friday, my friend, was born on friday".toUpperCase();

// The invocation above will return: "FRIDAY, MY FRIEND, WAS BORN ON FRIDAY"

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tip

To convert a JavaScript string to lowercase, use toLowerCase().

Overview​

String toUpperCase() method's tidbit

Use JavaScript's toUpperCase() method to convert your string to uppercase.

toUpperCase() returns the uppercase version of its calling string.