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We have to write a JavaScript function, say extract() that extracts properties from an object to another object and then deletes them from the original object.For example −If obj1 and obj2 are two objects, thenobj1 = {color:"red", age:"23", name:"cindy"} obj2 = extract(obj1, ["color", "name"])After passing through the extract function, they should become like −obj1 = { age:23 } obj2 = {color:"red", name:"cindy"}Therefore, let’s write the code for this function −Exampleconst obj = { name: "Rahul", job: "Software Engineer", age: 23, city: "Mumbai", hobby: "Reading books" }; const extract = (obj, ...keys) => { const ... Read More
We are required to write a function that returns true if the string in the first element of the array contains all of the letters of the string in the second element of the array.For example, ["hello", "Hello"], should return true because all of the letters in the second string are present in the first, ignoring their case.The arguments ["hello", "hey"] should return false because the string "hello" does not contain a "y".Lastly, ["Alien", "line"], should return true because all of the letters in "line" are present in "Alien".This is a fairly simple problem; we will just split the second ... Read More
Let’s say, we have an array of objects like this −const arr = [ {"name1": "firstString"}, {"name2": "secondString"}, {"name3": "thirdString"}, {"name4": "fourthString"}, {"name5": "fifthString"}, {"name6": "sixthString"}, ];We are required to write a function that takes one such array of objects and returns an object with all the properties listed in that object.So, let’s write the code for this function. It can be done through the Array reduce method −Exampleconst arr = [ {"name1": "firstString"}, {"name2": "secondString"}, {"name3": "thirdString"}, {"name4": "fourthString"}, {"name5": "fifthString"}, {"name6": "sixthString"}, ]; const reduceArray = ... Read More
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