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String: toUpperCase()

In addition to the length property, strings have methods. These are functions that are applied to the string. Like the length property, these methods are appended with a point to the string or to a variable that contains a string. The arguments enclosed in parentheses follow. Two of these string methods are the parameterless methods toUpperCase and toLowerCase. They return the string in uppercase or lowercase.
var town = 'Mthatha';
var output = town.toUpperCase();
output has the value 'MTHATHA'. town still has the value 'Mthatha'.
output = town.toLowerCase();
Now output has the value 'mthatha'.

Exercise

Write a function toCase that takes a string and returns that string in lowercase and uppercase with - as delimiter. toCase('Mthatha') should return 'mthatha-MTHATHA'.
var toCase = function(text) {
  return ... + '-' + ...;
};
var toCase = function(text) {
  return text.toLowerCase() + '-' + text.toUpperCase();
};