toUpperCase() is not making the string upper case

Question

I don't know what I'm doing wrong; But somehow .toUpperCase() String-function is not working on my browser or do I get something wrong?

var string ="kjsdgfiIJHBVSFIU";
string.toUpperCase();
console.log(string);

Live demo

Answer 1

.toUpperCase returns the upper-cased string. It is not an in-place modifier method.

string = string.toUpperCase();

Documentation: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/toUpperCase

Answer 2

String is Immutable. Once created, a string object can not be modified.

So here toUpperCase returns a new string, This should work-

var string ="kjsdgfiIJHBVSFIU";
var newString = string.toUpperCase();
alert(newString);