# 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 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.

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