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.]1. Write a JavaScript function to check whether an `input` is an array or not. Go to the editor
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. Go to the editor
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 a parameter 'n' will return the first 'n' elements of the array. Go to the editor
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 a parameter 'n' will return the last 'n' elements of the array. Go to the editor
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. Go to the editor
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 which accept a number as input and insert dashes (-) between each two even numbers. For example if you accept 025468 the output should be 0-254-6-8. Go to the editor
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7. Write a JavaScript program to sort the items of an array. Go to the editor
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 of an array. Go to the editor
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 which accept a string as input and swap the case of each character. For example if you input 'The Quick Brown Fox' the output should be 'tHE qUICK bROWN fOX'. Go to the editor
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10. Write a JavaScript program which prints the elements of the following array. Go to the editor
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 numeric vector. Go to the editor
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12. Write a JavaScript program to compute the sum and product of an array of integers. Go to the editor
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13. Write a JavaScript program to add items in an blank array and display the items. Go to the editor
Sample Screen :
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14. Write a JavaScript program to remove duplicate items from an array (ignore case sensitivity). Go to the editor
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15. We have the following arrays : Go to the editor
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. Go to the editor
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17. Write a JavaScript program to shuffle an array. Go to the editor
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18. Write a JavaScript program to perform a binary search. Go to the editor
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 from the given arrays. Go to the editor
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. Go to the editor
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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 a single level. Go to the editor
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. Go to the editor
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 of two arrays. Go to the editor
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. Go to the editor
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. Go to the editor
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. Write a JavaScript program to find a pair of elements (indices of the two numbers) from an given array whose sum equals a specific target number. Go to the editor
Input: numbers= [10,20,10,40,50,60,70], target=50
Output: 2, 3
27. Write a JavaScript function to retrieve the value of a given property from all elements in an array. Go to the editor
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. Go to the editor
Sample array : console.log(longest_common_starting_substring(['go', 'google']));
Expected result :
"go"
29. Write a JavaScript function to fill an array with values (numeric, string with one character) on supplied bounds. Go to the editor
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 to merge two arrays and removes all duplicates elements. Go to the editor
Test data :
var array1 = [1, 2, 3];
var array2 = [2, 30, 1];
console.log(merge_array(array1, array2));
[3, 2, 30, 1]
31. Write a JavaScript function to remove a specific element from an array. Go to the editor
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 contains a specific element. Go to the editor
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 keeping the original. Go to the editor
34. Write a JavaScript function to get nth largest element from an unsorted array. Go to the editor
Test Data :
console.log(nthlargest([ 43, 56, 23, 89, 88, 90, 99, 652], 4));
89
35. Write a JavaScript function to get a random item from an array. Go to the editor
36. Write a JavaScript function to create a specified number of elements with pre-filled numeric value array. Go to the editor
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. Write a JavaScript function to create a specified number of elements with pre-filled string value array. Go to the editor
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. Go to the editor
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. Go to the editor
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 specified length, filled with integer numbers, increase by one from starting position. Go to the editor
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. Go to the editor
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 the unique elements from two arrays. Go to the editor
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. Go to the editor
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. Go to the editor
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 unique values in an given array of numbers. Go to the editor
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 (contains duplicates). Go to the editor
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 falsy values from an given object or array. Go to the editor
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. Go to the editor
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. Go to the editor
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 calculate the sum of all numbers. Go to the editor
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. Go to the editor
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 of a given array of numbers and NaN. Go to the editor
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. Go to the editor
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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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.
JavaScript: Tips of the Day
Using the spread operator to combine objects
Let's say you want to combine multiple objects into one object containing them all.
The spread operator ( _ ) is a great way to achieve this!
const obj1 = {'a': 1, 'b': 2} const obj2 = {'c': 3} const obj3 = {'d': 4} // Combine them using the spread operator const objCombined = {...obj1, ...obj2, ...obj3} // Result: {'a': 1, 'b': 2, 'c': 3, 'd': 4}
Something to keep in mind while using this is that whenever you update one of the objects, it doesn't reflect those changes in the combined object.
Ref: https://bit.ly/2LBj213
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