How to create array as a property in javascript?

Question

I want to create a function that generates random Integers from a certain interval and each time it is called, it should produce a unique one. For that I have created this generateUniqueInt.

    function generateUniqueInt() {
        var res = Math.floor(Math.random() * 100);
        while (generateUniqueInt.used.indexOf(res) !== -1)
            res = Math.floor(Math.random() * 100);
        generateUniqueInt.used.push(res);
        return res;
    }
    generateUniqueInt.used = new Array;

    for (let i = 0; i < 20; i++) {
        console.log(generateUniqueInt());
    }

    generateUniqueInt.used.sort();
    console.log(generateUniqueInt.used);

I called this function few times like this and it works. Then I wanted to check which values were actually generated and for easier inspection I sorted the used property. But as it seems, used is not an array anymore.

I have tried using generateUniqueInt.used = []; as well as Object.defineProperty but the outcome is the same each time. What am I missing here? Is there a way to create used as an array?

I ran your code in chrome console and it worked for me, generateUniqueInt.used was an array with 20 values — TKoL
– TKoL, Commented Apr 9, 2018 at 16:01
That seems to be an interesting question, but the copy past of your code works just fine. — user10089632
– user10089632, Commented Apr 9, 2018 at 16:04
sort() sorts alphanumerically by default, ab > aa therefore 12 > 112. If you want to sort numerically: .sort((a,b) => a - b) — Jonas Wilms
– Jonas Wilms, Commented Apr 9, 2018 at 16:09

Rikin · Accepted Answer · 2018-04-09 16:23:10Z

2

Your issue is :The default sort order is according to string Unicode code points. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort

So below code will return following output:

var array1 = [1, 30, 4, 21];
array1.sort();
console.log(array1);
// expected output: Array [1, 21, 30, 4]

In order to solve for numbers you will may follow example from MDN:

var numbers = [4, 2, 5, 1, 3];
numbers.sort(function(a, b) {
  return a - b;
});
console.log(numbers);

// [1, 2, 3, 4, 5]

So your example would become following which should give you correct desired output:

generateUniqueInt.used.sort(function(a,b){ return a - b});

edited Apr 9, 2018 at 16:23

answered Apr 9, 2018 at 16:09

Rikin

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Taki · Accepted Answer · 2018-04-09 16:11:31Z

2

By default the sort method sorts elements alphabetically, so your array will be sorted like [1,2,25,3,4 ...]

use this to sort an array of numbers :

generateUniqueInt.used.sort(function(a,b){ return a - b});

let arr = [4,2,65,12,23,5,3]

let sorted1 = arr.sort()
console.log('sorted alphabetically : ', JSON.stringify(sorted1))

let sorted2 = arr.sort(function(a,b){ return a - b})
console.log('sorted numerically : ', JSON.stringify(sorted2))

answered Apr 9, 2018 at 16:11

Taki

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