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

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

Write a JavaScript program to get n random elements at unique keys from array up to the size of 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:

//#Source https://bit.ly/2neWfJ2 
const sampleSize = ([...arr], n = 1) => {
  let m = arr.length;
  while (m) {
    const i = Math.floor(Math.random() * m--);
    [arr[m], arr[i]] = [arr[i], arr[m]];
  }
  return arr.slice(0, n);
};

console.log(sampleSize([1, 2, 3], 2)); 
console.log(sampleSize([1, 2, 3], 4));

Sample Output:

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

Pictorial Presentation:

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

Flowchart:

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

Live Demo:

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


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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv