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JavaScript: Create an array of elements, ungrouping the elements in an array produced by zip and applying the provided function

JavaScript fundamental (ES6 Syntax): Exercise-106 with Solution

Write a JavaScript program to create an array of elements, ungrouping the elements in an array produced by zip and applying the provided function.

  • Use Math.max(), Function.prototype.apply() to get the longest subarray in the array, Array.prototype.map() to make each element an array.
  • Use Array.prototype.reduce() and Array.prototype.forEach() to map grouped values to individual arrays.
  • Use Array.prototype.map() and the spread operator (...) to apply fn to each individual group of elements.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const unzipWith = (arr, fn) =>
  arr
    .reduce(
      (acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),
      Array.from({
        length: Math.max(...arr.map(x => x.length))
      }).map(x => [])
    )
    .map(val => fn(...val));

console.log(unzipWith([[1, 10, 100], [2, 20, 200]], (...args) => args.reduce((acc, v) => acc + v, 0)));

Sample Output:

[3,30,300]

Pictorial Presentation:

JavaScript Fundamental: Return true if the given value is a number, false otherwise.

Flowchart:

flowchart: Create an array of elements, ungrouping the elements in an array produced by zip and applying the provided function

Live Demo:

See the Pen javascript-basic-exercise-106-1 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program that return true if the given value is a number, false otherwise.
Next: Write a JavaScript program to get all unique values (form the right side of the array) of an array, based on a provided comparator function.

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JavaScript: Tips of the Day

How to remove a specific item from an array?

Find the index of the array element you want to remove using indexOf, and then remove that index with splice.

The splice() method changes the contents of an array by removing existing elements and/or adding new elements.

const array = [2, 5, 9];

console.log(array);

const index = array.indexOf(5);
if (index > -1) {
  array.splice(index, 1);
}

// array = [2, 9]
console.log(array);

The second parameter of splice is the number of elements to remove. Note that splice modifies the array in place and returns a new array containing the elements that have been removed.

For the reason of completeness, here are functions. The first function removes only a single occurrence (i.e. removing the first match of 5 from [2,5,9,1,5,8,5]), while the second function removes all occurrences:

function removeItemOnce(arr, value) {
  var index = arr.indexOf(value);
  if (index > -1) {
    arr.splice(index, 1);
  }
  return arr;
}

function removeItemAll(arr, value) {
  var i = 0;
  while (i < arr.length) {
    if (arr[i] === value) {
      arr.splice(i, 1);
    } else {
      ++i;
    }
  }
  return arr;
}
//Usage
console.log(removeItemOnce([2,5,9,1,5,8,5], 5))
console.log(removeItemAll([2,5,9,1,5,8,5], 5))

Ref: https://bit.ly/2N9nKRp