SPREAD ARGUMENTS AND REST PARAMETERS

ECMAScript 6 introduces the spread operator, which allows for a very elegant way of managing and grouping collections. One of its most useful applications is in the domain of function signatures where it shines especially brightly in the domain of weak typing and variable length arguments. The spread operator is useful both when invoking a function, as well as when defining a function's parameters.

Spread Arguments

Instead of passing an array as a single function argument, it is often useful to be able to break apart an array of values and individually pass each value as a separate argument.

Suppose you have the following function defined, which sums all the values passed as arguments:

let values = [1, 2, 3, 4];

function getSum() {
 let sum = 0;
 for (let i = 0; i < arguments.length; ++i) {
  sum += arguments[i];
 }
 return sum;
}

This function expects each of its arguments to be an individual number that will be iterated through to find...