JS: String.prototype.toLowerCase

By Xah Lee. Date: 2017-12-28. Last updated: 2022-07-28.

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" );

str.toLowerCase()

Return a string of lower case version of string str.

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

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