Code golf reduce() in JavaScript.

reduce.js

// Impure
reduce = (f, i, l) => (n = [...l]).length ? r(f, f(i, n.pop()), n) : i

// Impure and minified
r=(f,i,l)=>(n=[...l]).length?r(f,f(i,n.pop()),n):i


// Pure
reduce = (reducerFunction, initialValue, enumerable) =>
  enumerable.length
  ? reduce(reducerFunction, reducerFunction(initialValue, enumerable[enumerable.length-1]), enumerable.slice(0, -1))
  : initialValue;

// Pure and minified
reduce = (f, i, l) => l.length ? reduce(f, f(i, l[l.length-1]), l.slice(0, -1)) : i