sort numbers from highest to lowest in javascript without using sort()

Question

const num = 12345

for (var i = 0; i < num.length; i++) {
  const j = i + 1
  if (num.charAt(i) < num.charAt(j)) {

    num.replace(i, j)
  }
}

console.log(num)

I'm trying to make a function that replace sort() method by javascript.

I want to sort my number from highest to lowest inside the variable num and return it after change. Here I'm using for loop with j so I'll be able to compare the indexes and change num but something wrong what do I miss?

I would love to keep it simple for my understanding.. thanks to the helpers!

You treat num like a string but it is a number. Use const num = "1234" — Titus
– Titus, Commented Aug 26, 2020 at 11:46
Why? what is wrong with sort? Is just an excercise, or does it have a serious use case? — Jan Stránský
– Jan Stránský, Commented Aug 26, 2020 at 11:51

angel.bonev · Accepted Answer · 2020-08-26 12:19:41Z

1

let num = 32145; // you can't change constants after declaration so we are using variables
num = num.toString(); // convert number to string
num = num.split(''); // split the number to array
//Bubble Sort starts here
var len = num.length;
for (var i = len - 1; i >= 0; i--) {
    for (var j = 1; j <= i; j++) {
        if (num[j - 1] > num[j]) {
            var temp = num[j - 1];
            num[j - 1] = num[j];
            num[j] = temp;
        }
    }
}
//Bubble Sort ends here
num = num.join(''); //convert array to string
num = parseInt(num); //convert string to number
console.log(num);

You can read more about these functions below

Number to string

String split

Array join

bubble sort function

ParseInt

edited Aug 26, 2020 at 12:19

answered Aug 26, 2020 at 12:08

angel.bonev

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3 Comments

BitterPirate Over a year ago

Thanks for the corrections, for the example and explanations, now it's clearer .. Thank you very much angel.bonev!

angel.bonev Over a year ago

@BitterPirate you're welcome I've added some extra links if you want to learn more about these functions

tonitone120 Over a year ago

@BitterPirate @angel.bonev One small edition I'd make is to simply print num.join(). The reason why is because if we have 0 somewhere in num, it'll get put to the start and parseInt() ignores numbers that have 0 at the start because numbers don't start with 0! ;)

Yogendra Chauhan · Accepted Answer · 2020-08-26 12:10:45Z

1

Here is the working example without javascript sort:

let num = "12345"
 
for (let j = 0; j < num.length - 1; j++) {
    for (let i = 0; i < num.length - 1; i++) {
      if (num[i] < num[i + 1]) {
        let temp = num[i + 1];
        num = num.replace(num[i+1], num[i]);
        num = num.replace(num[i], temp);
      }; 
    }; 
};
 
console.log(num);

answered Aug 26, 2020 at 12:10

Yogendra Chauhan

8255 silver badges15 bronze badges

Comments

Jay Parmar · Accepted Answer · 2020-08-26 11:52:32Z

0

You can do this sorting like this It's much simpler

const test = "124536"
const result = test.split('').sort().join('');

const test = "124536"

const result = test.split('').sort().join('');

console.log(result)

answered Aug 26, 2020 at 11:52

Jay Parmar

3782 silver badges9 bronze badges

2 Comments

freefaller Over a year ago

OP specifically said they didn't want to use .sort()

BitterPirate Over a year ago

thank jay, freefaller rights, without using sort but thank anyway..

ozgebykask · Accepted Answer · 2020-08-26 12:39:46Z

0

You can hold your numbers in an array if you want.

    var numbers= [1,2,3,4,5];
    for(i=0;i<numbers.length-1;i++){
        for(j=0;j<numbers.length-i-1;j++){
            if(numbers[j]<numbers[j+1]){
                var temp = numbers[j];
                numbers[j] = numbers[j+1];
                numbers[j+1] = temp;
            }
        }
    }
    console.log(numbers);

edited Aug 26, 2020 at 12:39

answered Aug 26, 2020 at 12:26

ozgebykask

993 bronze badges

Comments

tonitone120 · Accepted Answer · 2020-09-01 18:11:05Z

Reason why your code didn't work

You thought that num.replace(...) would actually change num. In JavaScript, primitive data-types (of which numbers are one of) cannot be changed. What num.replace(...) actually does is return a completely new string that is identical to num - except, of course, with the replacement.

function showLowestToHighest(num) {
    let numAsString = num.toString();
    let rawNumArray = [];
    for (const character of numAsString) {
        rawNumArray.push(Number.parseInt(character));
    }
    let sortedNumArray = [];

    for (let index = 0; index < numAsString.length; index++) {
        let smallestNum = Math.min(...rawNumArray);
        sortedNumArray.push(smallestNum);
        let smallestNumIndex = rawNumArray.indexOf(smallestNum);
        rawNumArray.splice(smallestNumIndex, 1);
    }
    console.log(sortedNumArray.join(''));
}

showLowestToHighest(894560);

How this function works

We establish rawNumArray - an array of the digits we're looking at. We then remove the smallest digit from rawNumArray and place it at the end of sortedNumArray, doing this until rawNumArray is empty. Finally, we log out the contents of sortedNumArray - as a string.

Weakness: if the number if larger then Number.MAX_SAFE_INTEGER it won't work.

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