JavaScript array - Exercises, Practice, Solution

JavaScript array [53 exercises with solution]

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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
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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]]
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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]
[]
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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]
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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"
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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.
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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
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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 )
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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'.
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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"
------
------
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11. Write a JavaScript program to find the sum of squares of a numerical vector.
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12. Write a JavaScript program to compute the sum and product of an array of integers.
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13. Write a JavaScript program to add items to a blank array and display them.
Sample Screen :

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14. Write a JavaScript program to remove duplicate items from an array (ignore case sensitivity).
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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.
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16. Write a JavaScript program to find the leap years in a given range of years.
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17. Write a JavaScript program to shuffle an array.
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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
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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]
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20. Write a JavaScript program to find duplicate values in a JavaScript array.
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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]
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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]
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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"]
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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]
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25. 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"
}]

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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

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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]
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28. 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"

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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"]

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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]

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

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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

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

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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]

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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"]
console.log(array_filled(4, 'password'));
["password", "password", "password", "password"]
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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]
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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]
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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]
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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]
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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"]
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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]]
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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"}}
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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]
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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]]
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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"}}
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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
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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
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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
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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
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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:
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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
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