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Let’s say, we have to write a function remove Nth that takes in an array and a number n and it removes every nth element of the array in place.This can be done using the Array.prototype.splice() method and here is the code for doing so −Exampleconst arr = ['T', 'h', 'a', 'i', 's', 'b', ' ', 'i', 'c', 's', ' ', 'a', 't', 'h', 'e', 'e', ' ', 't', 's', 'o', 'r', 'n', 'g', 't', ' ', 't', 'n', 'h', 'a', 's', 't', ' ', 'o', 'n', 'e', 'o', 'v', 'e', 'a', 'r', ' ', 'f', 'e', 'n', 'a', 'd', ... Read More
We have to write a function that returns the lowest index at which a value (second argument) should be inserted into an array (first argument) once it has been sorted (either in ascending or descending order). The returned value should be a number.For example, Let’s say, we have a function getIndexToInsert() −getIndexToInsert([1, 2, 3, 4], 1.5, ‘asc’) should return 1 because it is greater than 1 (index 0), but less than 2 (index 1).Likewise, getIndexToInsert([20, 3, 5], 19, ‘asc’) should return 2 because once the array has been sorted in ascending order it will look like [3, 5, 20] and ... Read More
We are required to write a JavaScript function, say checkThree() that takes in an array and returns true if anywhere in the array there exists three consecutive elements that are identical (i.e., have the same value) otherwise it returns false.Therefore, let’s write the code for this function −Exampleconst arr = ["g", "z", "z", "v" ,"b", "b", "b"]; const checkThree = arr => { const prev = { element: null, count: 0 }; for(let i = 0; i < arr.length; i++){ const { count, element } = prev; ... Read More
Consider the following binary array (Array A) −const arr = [1, 0, 1, 1, 1, 1, 0, 1, 1];When this array is passed through the function, say sumRight(), it produces the following output array (Array B) −const output = [1, 0, 4, 3, 2, 1, 0, 2, 1];Understanding the functionElements in array arr can be either 0 or 1. The function counts backward from the last element of array arr, if there are consecutive 1's in the array arr then the corresponding element in the output array will be 1 but for the 2nd consecutive 1 in array arr, it ... Read More
Let’s say. we have an array and an object like this −const arr = ['a', 'd', 'f']; const obj = { "a": 5, "b": 8, "c": 4, "d": 1, "e": 9, "f": 2, "g": 7 };We are required to write a function that takes in the object and the array and filter away all the object properties that are not an element of the array. So, the output should only contain 3 properties, namely: “a”, “d” and “e”.Let’s write the code for this function −Exampleconst arr = ['a', 'd', 'f']; const obj = ... Read More
We are required to write a sorting function that sort an array based on the contents of another array.For example − We have to sort the original array such that the elements present in the below sortOrder array appear right at the start of original array and all other should keep their order −const originalArray = ['Apple', 'Cat', 'Fan', 'Goat', 'Van', 'Zebra']; const sortOrder = ['Zebra', 'Van'];Exampleconst originalArray = ['Apple', 'Cat', 'Fan', 'Goat', 'Van', 'Zebra']; const sortOrder = ['Zebra', 'Van']; const sorter = (a, b) => { if(sortOrder.includes(a)){ return -1; }; if(sortOrder.includes(b)){ ... Read More
We are required to write a function that returns the index of the very first element that appears at least twice in the array. If no element appears more than once, we have to return -1. The condition is that we have to do this in constant space (i.e., without utilizing extra memory).Let’s devise the solution for this problem. We will use a for loop to iterate over the array and use the Array.prototype.lastIndexOf() method to check for duplicates.Exampleconst firstDuplicate = arr => { for(let i = 0; i < arr.length; i++){ if(arr.lastIndexOf(arr[i]) !== i){ ... Read More
We are required to write a function that takes in a one-dimensional array as the first argument and a number n as the second argument and we have to make n subarrays inside of the parent array (**if possible) and divide elements into them accordingly.** if the array contains 9 elements and we asked to make 4 subarrays, then dividing 2 elements in each subarray creates 5 subarrays and 3 in each creates 3, so in such cases we have to fallback to nearest lowest level (3 in this case) because our requirement is to distribute equal number of elements ... Read More
We are required to write a function, say isPowerOfTwo() that takes in a positive number and returns a boolean based on the fact whether or not the number is some power of 2.For example −console.log(isPowerOfTwo(3)); //false console.log(isPowerOfTwo(32)); //true console.log(isPowerOfTwo(2048)); //true console.log(isPowerOfTwo(256)); //true console.log(isPowerOfTwo(22)); //falseLet’s write the code for this function, it will be a very straightforward recursive function that keeps recurring until the number stays divisible by 2, if in this process the number gets reduced all the way down to 1, it is a power of 2 otherwise it isn’t. Here is the code −Exampleconst isPowerOfTwo = num => ... Read More
Let’s say, we are required to write a function classifyArray() that takes in an array which contains mixed data types and returns a Map() with the elements grouped by their data types.For example −// if the input array is: const arr = ['class', 2, [7, 8, 9], {"name": "Michael"}, Symbol('foo'), true, false, 'name', 6]; // then the output Map should be: Map(5) { 'string' => [ 'class', 'name' ], 'number' => [ 2, 6 ], 'object' => [ [ 7, 8, 9 ], { name: 'Michael' } ], 'symbol' => [ Symbol(foo) ], 'boolean' => ... Read More