JavaScript: Extract out the values at the specified indexes from a specified array

JavaScript fundamental (ES6 Syntax): Exercise-10 with Solution

Extract Values by Indexes from Array

Write a JavaScript program to extract values at specified indexes from a specified array.

• Use Array.prototype.filter() and Array.prototype.includes() to pull out the values that are not needed.
• Set Array.prototype.length to mutate the passed in an array by resetting its length to 0.
• Use Array.prototype.push() to re-populate it with only the pulled values.
• Use Array.prototype.push() to keep track of pulled values.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function called 'pull_at_Index' that takes two parameters: an array `arr` and an array of indices 'pullArr'.
const pull_at_Index = (arr, pullArr) => {
  // Initialize an empty array to store removed elements.
  let removed = [];
  // Filter the array 'arr' based on the indices specified in 'pullArr'.
  let pulled = arr
    .map((v, i) => (pullArr.includes(i) ? removed.push(v) : v)) // Push the elements at specified indices to 'removed' array.
    .filter((v, i) => !pullArr.includes(i)); // Filter out the elements at specified indices from 'arr'.
  // Clear the original array 'arr' and replace it with the filtered elements.
  arr.length = 0;
  pulled.forEach(v => arr.push(v));
  // Return the removed elements.
  return removed;
};

// Test cases
let arra1 = ['a', 'b', 'c', 'd', 'e', 'f'];
console.log(pull_at_Index(arra1, [1, 3])); // Output: ['b', 'd']
let arra2 =  [1, 2, 3, 4, 5, 6, 7];
console.log(pull_at_Index(arra2, [4])); // Output: [5]

Output:

["b","d"]
[5]

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-10 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that extracts values from an array based on a list of given indexes.
• Write a JavaScript function that returns a new array containing elements at specified positions from an input array.
• Write a JavaScript program that validates index bounds and then extracts corresponding elements from an array.

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