Generate Unique Numbers in Array

Question

I'm new to javascript and trying to get comfy with Functions, For loops, and If statements. I'm working on a simple exercise that generates 5 random numbers from a function call. One bit of logic that I'm struggling with putting together is comparing the numbers created by Math.random that are pushed into an array. What's the best method to use to ensure that all numbers to push to the array are unique (no duplicates)? Would I add an If statement in the For codeblock that checks every number, and if they match, rerun the Math.random function? Trying to figure out if that's the best way to approach the problem.

function randoNumbers(min, max){

let randomNumbers = [];

for (let counter = 0; counter < 5 ; counter++){
    randomNumbers.push(Math.floor(Math.random() * (max - min) + +min));
    }
    console.log(randomNumbers);

}

randoNumbers(1, 10);

Possible duplicate of Generate unique random numbers between 1 and 100 — Robby Cornelissen
– Robby Cornelissen, Commented Oct 23, 2018 at 3:30
Potential duplicate of stackoverflow.com/questions/2380019/… — Gaurav Suman
– Gaurav Suman, Commented Oct 23, 2018 at 3:39

CertainPerformance · Accepted Answer · 2018-10-23 03:30:21Z

2

A very plain solution would be to generate numbers until the generated number is not already included in the array, and then push it to the result array:

function randoNumbers(min, max) {
  const randomNumbers = [];
  for (let counter = 0; counter < 5; counter++) {
    let num;
    do {
      num = Math.floor(Math.random() * (max - min) + min);
    }
    while (randomNumbers.includes(num))
    randomNumbers.push(num);
  }
  console.log(randomNumbers);
}

randoNumbers(1, 10);

For slightly better complexity, you could use a Set instead (set.has is quicker than arr.includes):

function randoNumbers(min, max) {
  const set = new Set();
  for (let counter = 0; counter < 5; counter++) {
    let num;
    do {
      num = Math.floor(Math.random() * (max - min) + min);
    }
    while (set.has(num))
    set.add(num);
  }
  console.log([...set]);
}

randoNumbers(1, 10);

answered Oct 23, 2018 at 3:30

CertainPerformance

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4 Comments

RomeNYRR Over a year ago

This is great thank you! So overwhelmed with the fact that there are so many ways to solve this example. What's the best method for selecting the right approach, simplicity or complexity? I'll check out the includes function to better understand how the solution works

CertainPerformance Over a year ago

It depends on the situation, but ceteris paribus, simple is better, because code readability is one of the most important things to strive for. But, for example, if performance is a significant factor (which it rarely is), more complex code that runs more quickly can be worth it. (make sure to comment liberally if what the code is doing isn't obvious at a glance)

slider Over a year ago

Although, here I would argue that using a Set doesn't make the code any less readable and I would prefer it over using an array.

CertainPerformance Over a year ago

@slider Yep, it's not more complicated at all.

vijay krishna · Accepted Answer · 2018-10-23 03:44:55Z

2

There are many ways to solve this problem. I am contributing my way of solving it.

function randoNumbers(min, max) {

  let randomNumbers = [];

  for (; randomNumbers.length < 5;) {
    const value = Math.floor(Math.random() * (max - min) + +min);
    if (!randomNumbers.includes(value))
      randomNumbers.push(value);
  }
  console.log(randomNumbers);

}



randoNumbers(1, 10);

answered Oct 23, 2018 at 3:44

vijay krishna

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