freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-data-structures/combine-arrays-with-the-spread-operator.md

id, title, challengeType, forumTopicId

id	title	challengeType	forumTopicId
587d7b7b367417b2b2512b17	Combine Arrays with the Spread Operator	1	301156

Description

Another huge advantage of the spread operator, is the ability to combine arrays, or to insert all the elements of one array into another, at any index. With more traditional syntaxes, we can concatenate arrays, but this only allows us to combine arrays at the end of one, and at the start of another. Spread syntax makes the following operation extremely simple:

let thisArray = ['sage', 'rosemary', 'parsley', 'thyme'];

let thatArray = ['basil', 'cilantro', ...thisArray, 'coriander'];
// thatArray now equals ['basil', 'cilantro', 'sage', 'rosemary', 'parsley', 'thyme', 'coriander']

Using spread syntax, we have just achieved an operation that would have been more complex and more verbose had we used traditional methods.

Instructions

We have defined a function spreadOut that returns the variable sentence. Modify the function using the spread operator so that it returns the array ['learning', 'to', 'code', 'is', 'fun'].

Tests

tests:
  - text: <code>spreadOut</code> should return <code>["learning", "to", "code", "is", "fun"]</code>
    testString: assert.deepEqual(spreadOut(), ['learning', 'to', 'code', 'is', 'fun']);
  - text: The <code>spreadOut</code> function should utilize spread syntax
    testString: assert.notStrictEqual(spreadOut.toString().search(/[...]/), -1);

Challenge Seed

function spreadOut() {
  let fragment = ['to', 'code'];
  let sentence; // Change this line
  return sentence;
}

console.log(spreadOut());

Solution

function spreadOut() {
  let fragment = ['to', 'code'];
  let sentence = ['learning', ...fragment, 'is', 'fun'];
  return sentence;
}