# JavaScript array - Exercises, Practice, Solution

## JavaScript array [53 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts. Go to the editor]

1. Write a JavaScript function to check whether an `input` is an array or not.
Test Data :
console.log(is_array('w3resource'));
console.log(is_array([1, 2, 4, 0]));
false
true
Click me to see the solution

2. Write a JavaScript function to clone an array.
Test Data :
console.log(array_Clone([1, 2, 4, 0]));
console.log(array_Clone([1, 2, [4, 0]]));
[1, 2, 4, 0]
[1, 2, [4, 0]]
Click me to see the solution

3. Write a JavaScript function to get the first element of an array. Passing the parameter 'n' will return the first 'n' elements of the array.
Test Data :
console.log(first([7, 9, 0, -2]));
console.log(first([],3));
console.log(first([7, 9, 0, -2],3));
console.log(first([7, 9, 0, -2],6));
console.log(first([7, 9, 0, -2],-3));
Expected Output :
7
[]
[7, 9, 0]
[7, 9, 0, -2]
[]
Click me to see the solution

4. Write a JavaScript function to get the last element of an array. Passing the parameter 'n' will return the last 'n' elements of the array.
Test Data :
console.log(last([7, 9, 0, -2]));
console.log(last([7, 9, 0, -2],3));
console.log(last([7, 9, 0, -2],6));
Expected Output :
-2
[9, 0, -2]
[7, 9, 0, -2]
Click me to see the solution

5. Write a simple JavaScript program to join all elements of the following array into a string.
Sample array : myColor = ["Red", "Green", "White", "Black"];
Expected Output :
"Red,Green,White,Black"
"Red,Green,White,Black"
"Red+Green+White+Black"
Click me to see the solution

6. Write a JavaScript program that accepts a number as input and inserts dashes (-) between each even number. For example if you accept 025468 the output should be 0-254-6-8.
Click me to see the solution

7. Write a JavaScript program to sort the items of an array.
Sample array : var arr1 = [ -3, 8, 7, 6, 5, -4, 3, 2, 1 ];
Sample Output : -4,-3,1,2,3,5,6,7,8
Click me to see the solution

8. Write a JavaScript program to find the most frequent item in an array.
Sample array : var arr1=[3, 'a', 'a', 'a', 2, 3, 'a', 3, 'a', 2, 4, 9, 3];
Sample Output : a ( 5 times )
Click me to see the solution

9. Write a JavaScript program that accepts a string as input and swaps the case of each character. For example if you input 'The Quick Brown Fox' the output should be 'tHE qUICK bROWN fOX'.
Click me to see the solution

10. Write a JavaScript program that prints the elements of the following array.
Note : Use nested for loops.
Sample array : var a = [[1, 2, 1, 24], [8, 11, 9, 4], [7, 0, 7, 27], [7, 4, 28, 14], [3, 10, 26, 7]];
Sample Output :
"row 0"
" 1"
" 2"
" 1"
" 24"
"row 1"
------
------
Click me to see the solution

11. Write a JavaScript program to find the sum of squares of a numerical vector.
Click me to see the solution

12. Write a JavaScript program to compute the sum and product of an array of integers.
Click me to see the solution

13. Write a JavaScript program to add items to a blank array and display them.
Sample Screen :

Click me to see the solution

14. Write a JavaScript program to remove duplicate items from an array (ignore case sensitivity).
Click me to see the solution

15. We have the following arrays :
color = ["Blue ", "Green", "Red", "Orange", "Violet", "Indigo", "Yellow "];
o = ["th","st","nd","rd"]
Write a JavaScript program to display the colors in the following way :
"1st choice is Blue ."
"2nd choice is Green."
"3rd choice is Red."
- - - - - - - - - - - - -
Note : Use ordinal numbers to tell their position.
Click me to see the solution

16. Write a JavaScript program to find the leap years in a given range of years.
Click me to see the solution

17. Write a JavaScript program to shuffle an array.
Click me to see the solution

18. Write a JavaScript program to perform a binary search.
Note : A binary search or half-interval search algorithm finds the position of a specified input value within an array sorted by key value.
Sample array :
var items = [1, 2, 3, 4, 5, 7, 8, 9];
Expected Output :
console.log(binary_Search(items, 1)); //0
console.log(binary_Search(items, 5)); //4
Click me to see the solution

19. There are two arrays with individual values. Write a JavaScript program to compute the sum of each individual index value in the given array.
Sample array :
array1 = [1,0,2,3,4];
array2 = [3,5,6,7,8,13];
Expected Output :
[4, 5, 8, 10, 12, 13]
Click me to see the solution

20. Write a JavaScript program to find duplicate values in a JavaScript array.
Click me to see the solution

21. Write a JavaScript program to flatten a nested (any depth) array. If you pass shallow, the array will only be flattened to a single level.
Sample Data :
console.log(flatten([1, [2], [3, [[4]]],[5,6]]));
[1, 2, 3, 4, 5, 6]
console.log(flatten([1, [2], [3, [[4]]],[5,6]], true));
[1, 2, 3, [[4]], 5, 6]
Click me to see the solution

22. Write a JavaScript program to compute the union of two arrays.
Sample Data :
console.log(union([1, 2, 3], [100, 2, 1, 10]));
[1, 2, 3, 10, 100]
Click me to see the solution

23. Write a JavaScript function to find the difference between two arrays.
Test Data
:
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["3", "10", "100"]
console.log(difference([1, 2, 3, 4, 5], [1, [2], [3, [[4]]],[5,6]]));
["6"]
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["3", "10", "100"]
Click me to see the solution

24. Write a JavaScript function to remove. 'null', '0', '""', 'false', 'undefined' and 'NaN' values from an array.
Sample array : [NaN, 0, 15, false, -22, '',undefined, 47, null]
Expected result : [15, -22, 47]
Click me to see the solution

25. Write a JavaScript function to sort the following array of objects by title value.
Sample object :

```var library = [
{ author: 'Steve Jobs', title: 'Walter Isaacson', libraryID: 4264},
{ author: 'Suzanne Collins', title: 'Mockingjay: The Final Book of The Hunger Games', libraryID: 3245}
];
```

Expected result :

```[[object Object] {
author: "Suzanne Collins",
libraryID: 3245,
title:"Mockingjay:The Final Book of The Hunger Games"
}, [object Object] {
author: "Bill Gates",
libraryID: 1254,
}, [object Object] {
author: "Steve Jobs",
libraryID: 4264,
title: "Walter Isaacson"
}]
```

26. Write a JavaScript program to find a pair of elements (indices of the two numbers) in a given array whose sum equals a specific target number.

Input: numbers= [10,20,10,40,50,60,70], target=50
Output: 2, 3

Click me to see the solution

27. Write a JavaScript function to retrieve the value of a given property from all elements in an array.
Sample array : [NaN, 0, 15, false, -22, '',undefined, 47, null]
Expected result : [15, -22, 47]
Click me to see the solution

28. Write a JavaScript function to find the longest common starting substring in a set of strings.

Expected result : "go"

Click me to see the solution

29. Write a JavaScript function to fill an array with values (numeric, string with one character) within supplied bounds.

Test Data :
console.log(num_string_range('a', "z", 2));
["a", "c", "e", "g", "i", "k", "m", "o", "q", "s", "u", "w", "y"]

30. Write a JavaScript function that merges two arrays and removes all duplicate elements.

Test data :
var array1 = [1, 2, 3];
var array2 = [2, 30, 1];
console.log(merge_array(array1, array2));
[3, 2, 30, 1]

Click me to see the solution

31. Write a JavaScript function to remove a specific element from an array.

Test data :
console.log(remove_array_element([2, 5, 9, 6], 5));
[2, 9, 6]
Click me to see the solution

32. Write a JavaScript function to find an array containing a specific element.

Test data :
arr = [2, 5, 9, 6];
console.log(contains(arr, 5));
[True]
Click me to see the solution

33. Write a JavaScript script to empty an array while keeping the original.

34. Write a JavaScript function to get the nth largest element from an unsorted array.

Test Data :
console.log(nthlargest([ 43, 56, 23, 89, 88, 90, 99, 652], 4));
89

Click me to see the solution

35. Write a JavaScript function to get random items from an array.

Click me to see the solution

36. Write a JavaScript function to create a specified number of elements with a pre-filled numeric value array.

Test Data :
console.log(array_filled(6, 0));
[0, 0, 0, 0, 0, 0]
console.log(array_filled(4, 11));
[11, 11, 11, 11]

Click me to see the solution

37. Write a JavaScript function to create a specified number of elements with a pre-filled string value array.

Test Data :
console.log(array_filled(3, 'default value'));
["default value", "default value", "default value"]
Click me to see the solution

38. Write a JavaScript function to move an array element from one position to another.

Test Data :
console.log(move([10, 20, 30, 40, 50], 0, 2));
[20, 30, 10, 40, 50]
console.log(move([10, 20, 30, 40, 50], -1, -2));
[10, 20, 30, 50, 40]
Click me to see the solution

39. Write a JavaScript function to filter false, null, 0 and blank values from an array.

Test Data :
console.log(filter_array_values([58, '', 'abcd', true, null, false, 0]));
[58, "abcd", true]
Click me to see the solution

40. Write a JavaScript function to generate an array of integer numbers, increasing one from the starting position, of a specified length.

Test Data :
console.log(array_range(1, 4));
[1, 2, 3, 4]
console.log(array_range(-6, 4));
[-6, -5, -4, -3]
Click me to see the solution

41. Write a JavaScript function to generate an array between two integers of 1 step length.

Test Data :
console.log(rangeBetwee(4, 7));
[4, 5, 6, 7]
console.log(rangeBetwee(-4, 7));
[-4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7]
Click me to see the solution

42. Write a JavaScript function to find unique elements in two arrays.

Test Data :
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["1", "2", "3", "10", "100"]
console.log(difference([1, 2, 3, 4, 5], [1, [2], [3, [[4]]],[5,6]]));
["1", "2", "3", "4", "5", "6"]
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["1", "2", "3", "10", "100"]
Click me to see the solution

43. Write a JavaScript function to create an array of arrays, ungrouping the elements in an array produced by zip.

Test Data :
unzip([['a', 1, true], ['b', 2, false]])
unzip([['a', 1, true], ['b', 2]])
Expected Output:
[["a","b"],[1,2],[true,false]]
[["a","b"],[1,2],[true]]
Click me to see the solution

44. Write a JavaScript function to create an object from an array, using the specified key and excluding it from each value.

Test Data :
indexOn([ { id: 10, name: 'apple' }, { id: 20, name: 'orange' } ], x => x.id)
Expected Output:
{"undefined":{"id":20,"name":"orange"}}
Click me to see the solution

45. Write a JavaScript program to find all the unique values in a set of numbers.

Test Data :
[1, 2, 2, 3, 4, 4, 5]
[1, 2, 3, 4, 5]
[1, -2, -2, 3, 4, -5, -6, -5]
Expected Output:
[1,2,3,4,5]
[1,2,3,4,5]
[1,-2,3,4,-5,-6]
Click me to see the solution

46. Write a JavaScript program to generate all permutations of an array's elements (including duplicates).

Test Data :
[1, 33, 5]
[1, 3, 5, 7]
[2, 4]
Expected Output:
[[1,33,5],[1,5,33],[33,1,5],[33,5,1],[5,1,33],[5,33,1]]
[[1,3,5,7],[1,3,7,5],[1,5,3,7],[1,5,7,3],[1,7,3,5],[1,7,5,3],[3,1,5,7],[3,1,7,5],[3,5,1,7],[3,5,7,1],[3,7,1,5],[3,7,5,1],[5,1,3,7],[5,1,7,3],[5,3,1,7],[5,3,7,1],[5,7,1,3],[5,7,3,1],[7,1,3,5],[7,1,5,3],[7,3,1,5],[7,3,5,1],[7,5,1,3],[7,5,3,1]]
[[2,4],[4,2]]
Click me to see the solution

47. Write a JavaScript program to remove all false values from an object or array.

Test Data :
const obj = {
a: null,
b: false,
c: true,
d: 0,
e: 1,
f: '',
g: 'a',
h: [null, false, '', true, 1, 'a'],
i: { j: 0, k: false, l: 'a' }
Expected Output:
{"c":true,"e":1,"g":"a","h":[true,1,"a"],"i":{"l":"a"}}
Click me to see the solution

48. Write a JavaScript program that takes an array of integers and returns false if every number is not prime. Otherwise, return true.

Test Data :
([2,3,5,7]) -> true
([2,3,5,7,8]) -> false
Expected Output:
Original array of integers: 2,3,5,7
In the said array check every numbers are prime or not! true
Original array of integers: 2,3,5,7,8
In the said array check every numbers are prime or not! false
Click me to see the solution

49. Write a JavaScript program that takes an array of numbers and returns the third smallest number.

Test Data :
(2,3,5,7,1) -> 3
(2,3,0,5,7,8,-2,-4) -> 0
Expected Output:
Original array of numbers: 2,3,5,7,1
Third smallest number of the said array of numbers: 3
Original array of numbers: 2,3,0,5,7,8,-2,-4
Third smallest number of the said array of numbers: 0
Click me to see the solution

50. Write a JavaScript program that takes an array with mixed data type and calculates the sum of all numbers.

Test Data :
([2, "11", 3, "a2", false, 5, 7, 1]) -> 18
([2, 3, 0, 5, 7, 8, true, false]) -> 25
Expected Output:
Original array: 2,11,3,a2,false,5,7,1
Sum all numbers of the said array: 18
Original array: 2,3,0,5,7,8,true,false
Sum all numbers of the said array: 25
Click me to see the solution

51. Write a JavaScript program to check if an array is a factor chain or not.

A factor chain is an array in which the previous element is a factor of the next consecutive element. The following is a factor chain:
[2, 4, 8, 16, 32]
// 2 is a factor of 4
// 4 is a factor of 8
// 8 is a factor of 16
// 16 is a factor of 32

Test Data :
([2, 4, 8, 16, 32]) -> true
([2, 4, 16, 32, 64]) -> true
([2, 4, 16, 32, 68]) -> false
Expected Output:
Original array:
Check the said array is a factor chain or not?
true
Original array:
Check the said array is a factor chain or not?
true
Original array:
Check the said array is a factor chain or not?
false
Click me to see the solution

52. Write a JavaScript program to get all the indexes where NaN is found in a given array of numbers and NaN.

Test Data :
([2, NaN, 8, 16, 32]) -> [1]
([2, 4, NaN, 16, 32, NaN]) -> [2,5]
([2, 4, 16, 32]) ->[]
Expected Output:
Original array: 2,NaN,8,16,32
Find all indexes of NaN of the said array: 1
Original array: 2,4,NaN,16,32,NaN
Find all indexes of NaN of the said array: 2,5
Original array: 2,4,16,32
Find all indexes of NaN of the said array:
Click me to see the solution

53. Write a JavaScript program to count the number of arrays inside a given array.

Test Data :
([2,8,[6],3,3,5,3,4,[5,4]]) -> 2
([2,8,[6,3,3],[4],5,[3,4,[5,4]]]) -> 3
Expected Output:
Number of arrays inside the said array: 2
Number of arrays inside the said array: 3
Click me to see the solution

More to Come !

Live Demo

* To run the code mouse over on Result panel and click on 'RERUN' button.*

See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.

Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.

﻿