JavaScript array - Exercises, Practice, Solution
This resource offers a total of 265 JavaScript array problems for practice. It includes 53 main exercises, each accompanied by solutions, detailed explanations, and four related problems.
[An Editor is available at the bottom of the page to write and execute the scripts.]
1. Check Array Input
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
2. Clone Array
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]]
3. First Elements of Array
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]
[]
4. Last Elements of Array
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]
5. Join Array Elements
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"
6. Insert Dashes Between Evens
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.
7. Sort Array
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
8. Most Frequent Array Item
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 )
9. Swap Case in String
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'.
10. Print Nested Array Elements
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"
------
------
11. Sum of Squares in Array
Write a JavaScript program to find the sum of squares of a numerical vector.
12. Sum and Product of Array
Write a JavaScript program to compute the sum and product of an array of integers.
13. Add Items to Array
Write a JavaScript program to add items to a blank array and display them.
Sample Screen :
Click me to see the solution
14. Remove Duplicates
Write a JavaScript program to remove duplicate items from an array (ignore case sensitivity).
15. Display Colors with Ordinals
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.
16. Find Leap Years in Range
Write a JavaScript program to find the leap years in a given range of years.
17. Shuffle Array
Write a JavaScript program to shuffle an array.
18. Binary Search
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
19. Sum of Arrays by Index
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]
20. Find Duplicate Values
Write a JavaScript program to find duplicate values in a JavaScript array.
21. Flatten Nested Array
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]
22. Union of Two Arrays
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]
23. Difference Between Arrays
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"]
24. Remove Falsy Values
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]
25. Sort Objects by Title
Write a JavaScript function to sort the following array of objects by title value.
Sample object :
var library = [
{ author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254},
{ 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,
title: "The Road Ahead"
}, [object Object] {
author: "Steve Jobs",
libraryID: 4264,
title: "Walter Isaacson"
}]
26. Find Pair with Target Sum
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
27. Retrieve Property Values
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]
28. Longest Common Starting Substring
Write a JavaScript function to find the longest common starting substring in a set of strings.
Sample array : console.log(longest_common_starting_substring(['go', 'google']));
Expected result : "go"
29. Fill Array with Values
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. Merge Arrays Without Duplicates
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]
31. Remove Specific Element
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]
32. Find Element in Array
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]
33. Empty Array
Write a JavaScript script to empty an array while keeping the original.
34. Nth Largest Element
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
35. Random Array Item
Write a JavaScript function to get random items from an array.
36. Pre-filled Numeric Array
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]
37. Pre-filled String Array
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"]
console.log(array_filled(4, 'password'));
["password", "password", "password", "password"]
38. Move Array Element
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]
39. Filter Array Values
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]
40. Generate Integer Range Array
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]
41. Array Between Two Integers
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]
42. Unique Elements from Two Arrays
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"]
43. Unzip Arrays
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]]
44. Object from Array with Key
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"}}
45. Unique Values in Array
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]
46. Permutations of Array Elements
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]]
47. Remove Falsey from Object or Array
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"}}
48. Check All Numbers Prime
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
49. Find Third Smallest Number
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
50. Sum Numbers in Mixed Array
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
51. Check Factor Chain
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
52. Find NaN Indexes in Array
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:
53. Count Arrays Inside Array
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
More to Come !
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