Arrays

Question 1

Arrays that only have one level, or that it does not have any other arrays nested within it.

Answer 1

One-dimensional array

Question 2

An array that contains other arrays

Answer 2

Multi-dimensional array

Question 3

The method that adds elements to the end of an array

Answer 3

push() method

Question 4

The method that adds elements to the beginning

Answer 4

unshift() method

Question 5

The method that removes an element from the end of an array

Answer 5

pop() method

Question 6

The method that removes an element from the beginning of an array.

Answer 6

shift() method

Question 7

The method that remove any number of consecutive elements from anywhere in an array.

Answer 7

splice()

Question 8

map()

Answer 8

Creates a new array with the results of calling a provided function on every element in the calling array.
(It performs a function on every element of the array and results in a new array)
eg.)
var array1 = [1, 4, 9, 16];

// pass a function to map
const map1 = array1.map(x => x * 2);

console.log(map1);
// expected output: Array [2, 8, 18, 32]

Question 9

find()

Answer 9

The find() method returns the value of the first element in the array that satisfies the provided testing function. Otherwise undefined is returned.
(It performs the given function to the array and spits back the first true element)
eg.)
var array1 = [5, 12, 8, 130, 44];

var found = array1.find(function(element) {
  return element > 10;
});

console.log(found);
// expected output: 12

Question 10

findIndex()

Answer 10

The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise, it returns -1, indicating that no element passed the test.
eg.)
var array1 = [5, 12, 8, 130, 44];

function isLargeNumber(element) {
  return element > 13;
}

console.log(array1.findIndex(isLargeNumber));
// expected output: 3

Question 11

filter()

Answer 11

The filter() method creates a new array with all elements that pass the test implemented by the provided function.
eg.)
var words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6);

console.log(result);
// expected output: Array ["exuberant", "destruction", "present"]

Question 12

reduce()

Answer 12

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in a single output value.
eg.) const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;

// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10

// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15

Question 13

concat()

Answer 13

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
eg.)
var array1 = ['a', 'b', 'c'];
var array2 = ['d', 'e', 'f'];

console.log(array1.concat(array2));
// expected output: Array ["a", "b", "c", "d", "e", "f"]

Question 14

slice()

Answer 14

The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.
eg.) 
var animals = ['ant', 'bison', 'camel', 'duck', 'elephant'];

console.log(animals.slice(2));
// expected output: Array ["camel", "duck", "elephant"]

console.log(animals.slice(2, 4));
// expected output: Array ["camel", "duck"]

console.log(animals.slice(1, 5));
// expected output: Array ["bison", "camel", "duck", "elephant"]

Question 15

splice()

Answer 15

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.
eg.)
var months = [‘Jan’, ‘March’, ‘April’, ‘June’];
months.splice(1, 0, ‘Feb’);
// inserts at index 1
console.log(months);
// expected output: Array [‘Jan’, ‘Feb’, ‘March’, ‘April’, ‘June’]

months.splice(4, 1, ‘May’);
// replaces 1 element at index 4
console.log(months);
// expected output: Array [‘Jan’, ‘Feb’, ‘March’, ‘April’, ‘May’]