The toLocaleLowerCase() converts the string into lowercase as toLowerCase method but based on locale settings on the browser.
Syntax
String.toLocaleLowerCase()
Example
var s1 = 'HELLO';
var s2 = 'Hello';
var s3 = 'hElLo';
document.write(s1.toLocaleLowerCase());
document.write(s2.toLocaleLowerCase());
document.write(s3.toLocaleLowerCase());