Uppercasing a String

Problem

You want to uppercase a string.

Solution

Use JavaScript’s String toUpperCase() method:

"one two three".toUpperCase()
# => 'ONE TWO THREE'

Discussion

toUpperCase() is a standard JavaScript method. Don’t forget the parentheses.

Syntax Sugar

You can add some Ruby-like syntax sugar with the following shortcut:

String::upcase = -> @toUpperCase()
"one two three".upcase()
# => 'ONE TWO THREE'

The snippet above demonstrates a few features of CoffeeScript:

• The double-colon :: is shorthand for saying .prototype.
• The “at” sign @ is shorthand for saying this.

The code above compiles in to the following JavaScript:

String.prototype.upcase = function() {
  return this.toUpperCase();
};
"one two three".upcase();

Note: Although it’s quite common in languages like Ruby, extending native objects is often considered bad practice in JavaScript (see: Maintainable JavaScript: Don’t modify objects you don’t own; Extending built-in native objects. Evil or not?).