How to Improve Random Number Generation in JavaScript for Unique and Non-Repeating Results?

Generating Unique Random Numbers in JavaScript

In JavaScript, generating non-repeating random numbers presents challenges, as exemplified by the error report in Chrome. The function presented in the question necessitates improvements to ensure unique numbers.

Alternative Approach 1: Random Permutation

To avoid invoking the random number function repeatedly, it's advisable to generate a random permutation of numbers initially. The following code snippet achieves this for numbers between 1 and 10:

var nums = [1,2,3,4,5,6,7,8,9,10],
    ranNums = [],
    i = nums.length,
    j = 0;

while (i--) {
    j = Math.floor(Math.random() * (i+1));
    ranNums.push(nums[j]);
    nums.splice(j,1);
}

This approach eliminates the risk of elongated processing time to find unused numbers.

Alternative Approach 2: Fisher–Yates Shuffle

A more efficient method known as the Fisher–Yates Shuffle can be employed:

function shuffle(array) {
    var i = array.length,
        j = 0,
        temp;

    while (i--) {

        j = Math.floor(Math.random() * (i+1));

        // swap randomly chosen element with current element
        temp = array[i];
        array[i] = array[j];
        array[j] = temp;

    }

    return array;
}

var ranNums = shuffle([1,2,3,4,5,6,7,8,9,10]);

Alternative Approach 3: Generators

Another option is to utilize generators:

function* shuffle(array) {

    var i = array.length;

    while (i--) {
        yield array.splice(Math.floor(Math.random() * (i+1)), 1)[0];
    }

}

To use:

var ranNums = shuffle([1,2,3,4,5,6,7,8,9,10]);

ranNums.next().value;    // first random number from array
ranNums.next().value;    // second random number from array
ranNums.next().value;    // etc.

The choice of approach depends on the specific requirements and constraints of the application.

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