JavaScript String.toUpperCase() Method

The toUpperCase() method is useful when developers want to toggle the case of the lowercase characters to uppercase. Given that JavaScript strings are immutable, the toUpperCase() method does not affect the string’s actual value.

The value will be transformed to a string if it is not already one via the toUpperCase() method, which returns the calling string value in uppercase.

Syntax of JavaScript toUpperCase():

string.toUpperCase();

Parameter

This method does not take any parameters.

Return

It converts the string’s case to uppercase.

Example Codes: Convert All Lowercase Strings to Uppercase

The toUpperCase() method converts the entire string to uppercase. This method does not affect any special characters or numbers already in uppercase.

In this demonstration, all lowercase characters in a string have been changed to uppercase. The method toUpperCase() turns every character of string input into uppercase characters, which we can see in the below example output.

var referenceString = 'javascript is best for gamers';
var str = referenceString.toUpperCase();
console.log(str);

Output:

JAVASCRIPT IS BEST FOR GAMERS

Example Codes: Convert Toggle Case String to Uppercase

A string with alternate lowercase and uppercase letters is known as a toggle case string. The below example demonstrates how to change a string of characters from lowercase to uppercase.

You can see in the output that the method toUpperCase() converts all toggle case characters in a string to uppercase.

var str = 'JavAScRipT is A gOOd ProgRamMinG LanGuaGe';
var result = str.toUpperCase();
console.log(result);

Output:

JAVASCRIPT IS A GOOD PROGRAMMING LANGUAGE

Example Codes: Convert a String With Digits and Special Characters to Uppercase

This technique converts all lowercase alphabets to the corresponding uppercase equivalents without affecting the numerals or special characters.

In this illustration, the string st contains lowercase and uppercase letters, digits, and special characters. All of the lowercase letters have been changed to uppercase.

var st = 'This was a GrE@t 15 mInute Run';
var result = st.toUpperCase();
console.log(result);

Output:

THIS WAS A GRE@T 15 MINUTE RUN

The toUpperCase() method is supported by most modern browsers. Use the toUpperCase method to convert a string with uppercase, lowercase, numerals, or special characters to uppercase.