undefined elements inside an array which has randomized numbers inside it

Question

so I created this script to generate an array of 5 random numbers where the numbers must be unique, but I get +2 undefined elements. There are 5 numbers which are unique but the length of the array isn't anymore 5

let arr = [];
while (arr.length <= 5) {
  let x = Math.floor(Math.random() * 11);
  if (arr.includes(x) === false) {
    arr.push(x);
  }
  arr.length += 1;
}
console.log(arr);

Thanks in advance guys.

`arr.length += 1;` Your push is going to increase the length, so no need to do this. — Keith, Jan 27 '21 at 21:54
This is a bad way to do it. Make an array of all the numbers. Shuffle the array. Take the first 5 elements. — Barmar, Jan 27 '21 at 21:56
Does this answer you question :) https://stackoverflow.com/questions/5836833/create-an-array-with-random-values — Imran Rafiq Rather, Jan 27 '21 at 21:59

score 2 · Accepted Answer · answered Jan 27 '21 at 21:55

2

You should remove the arr.length += 1 line. The array length will be automatically incremented each time a new element is pushed, no need to modify it by yourself: this is a bad practice.

answered Jan 27 '21 at 21:55

David Fernández Ortiz

691
4
7

1

I didn't notice that, thanks for your quick response man! – makar0v Jan 28 '21 at 17:40

score 1 · Answer 2 · answered Jan 27 '21 at 21:59

1

the length is not 5 because this loop runs 6 times, arr.length = 0,1,2,3,4,5. and you have a 3 undefined elements because of ( arr.length += 1; ) this skips step 1,3,5.

answered Jan 27 '21 at 21:59

Am Ben

89
5

score 0 · Answer 3 · answered Jan 27 '21 at 22:00

0

let arr = [];   
while (arr.length<5){
 let x = Math.floor(Math.random()*11);
 if (arr.includes(x) === false){
     arr.push(x);
}
}
console.log(arr);

answered Jan 27 '21 at 22:00

Mohamed Ghoneim

153
6

undefined elements inside an array which has randomized numbers inside it

3 Answers3