JavaScript: Get n random elements at unique keys from array up to the size of array

JavaScript fundamental (ES6 Syntax): Exercise-226 with Solution

n Random Unique Elements

Write a JavaScript program to get n random elements with unique keys from an array up to the size of the array.

• Shuffle the array using the Fisher-Yates algorithm.
• Use Array.prototype.slice() to get the first n elements.
• Omit the second argument, n, to get only one element at random from the array.

Sample Solution:

JavaScript Code:

// Define a function 'sampleSize' to randomly sample elements from an array
const sampleSize = ([...arr], n = 1) => {
  let m = arr.length;
  
  // Shuffle the array using the Fisher-Yates algorithm
  while (m) {
    const i = Math.floor(Math.random() * m--);
    [arr[m], arr[i]] = [arr[i], arr[m]];
  }
  
  // Return a slice of the shuffled array with 'n' elements
  return arr.slice(0, n);
};

// Log the result of sampling 2 elements from an array
console.log(sampleSize([1, 2, 3], 2));  
// Log the result of sampling 4 elements from an array (exceeding the array length)
console.log(sampleSize([1, 2, 3], 4));

Output:

[3,2]
[2,3,1]

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-226-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns n random elements from an array ensuring no duplicates are selected.
• Write a JavaScript function that shuffles an array and then extracts the first n elements for uniqueness.
• Write a JavaScript program that uses a Set to keep track of chosen elements until n unique items are gathered.
• Write a JavaScript function that validates n against the array length and returns an array of n unique random items.

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