freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/basic-data-structures/copy-array-items-using-slice.english.md

id, title, challengeType

id	title	challengeType
587d7b7a367417b2b2512b12	Copy Array Items Using slice()	1

Description

The next method we will cover is slice(). slice(), rather than modifying an array, copies, or extracts, a given number of elements to a new array, leaving the array it is called upon untouched. slice() takes only 2 parameters — the first is the index at which to begin extraction, and the second is the index at which to stop extraction (extraction will occur up to, but not including the element at this index). Consider this:

let weatherConditions = ['rain', 'snow', 'sleet', 'hail', 'clear'];

let todaysWeather = weatherConditions.slice(1, 3);
// todaysWeather equals ['snow', 'sleet'];
// weatherConditions still equals ['rain', 'snow', 'sleet', 'hail', 'clear']

In effect, we have created a new array by extracting elements from an existing array.

Instructions

We have defined a function, forecast, that takes an array as an argument. Modify the function using slice() to extract information from the argument array and return a new array that contains the elements 'warm' and 'sunny'.

Tests

tests:
  - text: <code>forecast</code> should return <code>["warm", "sunny"]</code>
    testString: assert.deepEqual(forecast(['cold', 'rainy', 'warm', 'sunny', 'cool', 'thunderstorms']), ['warm', 'sunny']);
  - text: The <code>forecast</code> function should utilize the <code>slice()</code> method
    testString: assert(/\.slice\(/.test(code));

Challenge Seed

function forecast(arr) {
  // change code below this line

  return arr;
}

// do not change code below this line
console.log(forecast(['cold', 'rainy', 'warm', 'sunny', 'cool', 'thunderstorms']));

Solution

function forecast(arr) {
  return arr.slice(2,4);
}