JavaScript: String.prototype.toLowerCase

toUpperCase

str.toUpperCase()

Return a string of upper case version of string str.

works on Greek or any unicode that has upper/lower case defined.

console.log( "abc".toUpperCase() === "ABC" );
console.log( "δγπ".toUpperCase() === "ΔΓΠ" );

toLowerCase

str.toLowerCase()

Return a string of lower case version of string str.

console.log( "ABC".toLowerCase() === "abc" );
console.log( "ΔΓΠ".toLowerCase() === "δγπ" );

toLocaleUpperCase, toLocaleLowerCase

str.toLocaleUpperCase()

same as str.toUpperCase(), except that it may be different in some languages (for example, Turkish). JavaScript implementation may not chose to have this behavior. In that case, its identical to str.toUpperCase().