JavaScript: Inverse letter case

invertCase.js

Implement and export as default a function that changes the case of each letter in the string to the opposite.

Examples:

invertCase('Hello, World!'); // hELLO, wORLD!
invertCase('I loVe JS');     // i LOvE js

Tips

• To find out the length of a string, use the length property:

'welcome'.length; // 7

• To convert a string (or a single character) to uppercase, use the toUpperCase() method:

'foo'.toUpperCase(); // 'FOO';
'f'.toUpperCase();   // 'F';

• To convert a string (or a single character) to lowercase, use the toLowerCase() method

'BAR'.toLowerCase(); // 'bar';
'b'.toLowerCase();   // 'b';