def document(f): def wrap(x): print "I am going to square", x f(x) return wrap @document def square(x): print math.pow(x, 2) square(5)

Since 'using decorators' has come to mean 'smothering your code in @ symbols' it's probably no longer a great name.

// Rewrite submit function form.submit = () => { const result = originalSubmit.call(form)

Does it look like a decorator plugin in Ractive, right

Middleware works a lot like a decorator. It doesn't alter the original API of the service, but it can augment it with new features and concerns. This has the inherent advantage of allowing all thidparty code to have an influence over the behaviour, state, and UI of a component.