freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/use-the-rest-parameter-with-function-parameters.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
587d7b88367417b2b2512b47	Use the Rest Parameter with Function Parameters	1	301221	use-the-rest-parameter-with-function-parameters

--description--

In order to help us create more flexible functions, ES6 introduces the rest parameter for function parameters. With the rest parameter, you can create functions that take a variable number of arguments. These arguments are stored in an array that can be accessed later from inside the function.

Check out this code:

function howMany(...args) {
  return "You have passed " + args.length + " arguments.";
}
console.log(howMany(0, 1, 2));
console.log(howMany("string", null, [1, 2, 3], { }));

The console would display the strings You have passed 3 arguments. and You have passed 4 arguments..

The rest parameter eliminates the need to check the args array and allows us to apply map(), filter() and reduce() on the parameters array.

--instructions--

Modify the function sum using the rest parameter in such a way that the function sum is able to take any number of arguments and return their sum.

--hints--

The result of sum(0,1,2) should be 3

assert(sum(0, 1, 2) === 3);

The result of sum(1,2,3,4) should be 10

assert(sum(1, 2, 3, 4) === 10);

The result of sum(5) should be 5

assert(sum(5) === 5);

The result of sum() should be 0

assert(sum() === 0);

sum should be an arrow function which uses the rest parameter syntax (...) on the args parameter.

assert(__helpers.removeWhiteSpace(code).match(/sum=\(\.\.\.args\)=>/));

--seed--

--seed-contents--

const sum = (x, y, z) => {
  const args = [x, y, z];
  return args.reduce((a, b) => a + b, 0);
}

--solutions--

const sum = (...args) => {
  return args.reduce((a, b) => a + b, 0);
}