Javascript bubble sort of an array with objects

Question

beginner here!

Recently stumbled upon a problem. Basically, the program needs to sort an array of objects by one of their fields without actually using the sort function. I've tried this code using bubble sort algorithm, but it doesn't seem to be working:

var arrayOfPeople = [
    {name: "Rick", age: 30, place: 2},
    {name: "Alan", age: 25, place: 1},
    {name: "Joe", age: 40, place: 4},
    {name: "Dave", age: 35, place: 3}
];


function bubbleSort(a,par)
{
    var swapped;

    do {
        swapped = false;

        for (var i = 0; i < a.length - 1; i++) {
            if (a[i].par > a[i + 1].par) {
                var temp = a[i];

                a[i] = a[i + 1];
                a[i + 1] = temp;

                swapped = true;
            }
        }
    } while (swapped);
}


bubbleSort(arrayOfPeople,'age');

for (i = 0; i < arrayOfPeople.length; i++) {
    console.log(arrayOfPeople[i]);
}

My guess is that I'm doing something wrong syntax-wise. Will appreciate any feedback.

It might be that you haven't initialized you swapped-variable befor the do-while loop starts. Try replacing var swapped with var swapped = false — mfaerevaag
– mfaerevaag, Commented Jun 6, 2013 at 8:00
Use native sort will be faster stackoverflow.com/a/1129270/1346222 — b1_
– b1_, Commented Jun 6, 2013 at 9:15

Community · Accepted Answer · 2020-06-20 09:12:55Z

7

The only problem was that you were not using the "par" argument correctly. The obj.prop syntax will always try to look for property named "prop" so to have it dynamic you need to use square brackets e.g. obj["prop"] which can get variable instead of "prop".

You didn't get any errors as a[i].par and a[i+1].par both returned undefined which can be compared to itself. (hence a[i].par > a[i+1].par always returns false)

Here is revised code that works:

function bubbleSort(a, par)
{
    var swapped;
    do {
        swapped = false;
        for (var i = 0; i < a.length - 1; i++) {
            if (a[i][par] > a[i + 1][par]) {
                var temp = a[i];
                a[i] = a[i + 1];
                a[i + 1] = temp;
                swapped = true;
            }
        }
    } while (swapped);
}


bubbleSort(arrayOfPeople, 'age');

for (i = 0; i < arrayOfPeople.length; i++) {
   console.log(arrayOfPeople[i]);
}

Live test case.

Worth to mention in this context, that the function changing the actual object (array in this case) is not a trivial thing. To learn more what is passed by value and what is passed by reference take a look in this excellent question: Is JavaScript a pass-by-reference or pass-by-value language?

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Jun 6, 2013 at 8:03

user447356

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3 Comments

Alexander Pavlov Over a year ago

Can you clarify your first statement (JavaScript has no "by reference" for function arguments)? a is definitely passed into bubbleSort by reference, or do you imagine that it is copied, and a copy thereof is passed into bubbleSort instead? Sorting the array in-place inside bubbleSort will definitely work.

user447356 Over a year ago

@AlexanderPavlov blonde moment/ignorance on my part you're totally correct. I have revised my answer. Thanks! :)

Alexander Pavlov Over a year ago

np. Great answer otherwise!

TheSavage · Accepted Answer · 2014-01-18 21:59:17Z

5

Use the built in array sort function:

arrayOfPeople.sort(function(a,b) {return a.age-b.age;});

answered Jan 18, 2014 at 21:59

TheSavage

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