Can someone please explain what is happening in this code?

Question

1.00/5 (2 votes)

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JavaScript

<!DOCTYPE html>



<p>Click the buttons to sort car objects on type.</p>

Sort

<p id="demo"></p>
<p id="dd"> </p>
<p id="ddd"> </p>



var cars = [
{type:"Volvo", year:2016},
{type:"Saab", year:2001},
{type:"BMW", year:2010}]

displayCars();

function myFunction() {
    cars.sort(function(a, b){
        var x = a.type.toLowerCase();
        var y = b.type.toLowerCase();
        document.getElementById("dd").innerHTML= x;
        document.getElementById("ddd").innerHTML = y;
        if (x &lt; y) {return 0;}
        if (x > y) {return 1;}
        });
    displayCars();
}

function displayCars() {
  document.getElementById("demo").innerHTML =
  cars[0].type + " " + cars[0].year + "<br>" +
  cars[1].type + " " + cars[1].year + "<br>" +
  cars[2].type + " " + cars[2].year;
}

What I have tried:

I just want to know about why .tolowercase is used here with return (0) or (1).

Posted 29-Apr-17 22:38pm

Thenewbieee

Updated 30-Apr-17 3:58am

Patrice T

v3

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OriginalGriff · Accepted Answer · 2017-04-29T22:51:00

Solution 1

tolowercase is used to ensure that the comparison is always comparing the same values: in computer terms, "Hello" is not the same as "hello" because upper and lower case characters are not the same, 'H' is not the same characters as 'h'.

The return values indicates the sort order: 0 means the second parameter is the largest, 1 means the first is. If they are both the same, a random value it returns, and will cause bugs later on...

Posted 29-Apr-17 22:51pm

OriginalGriff

Updated 29-Apr-17 22:53pm

v2

Comments

Thenewbieee 30-Apr-17 5:03am

I still can't get it, can you please explain the lines of myfunction() ?

Thenewbieee 30-Apr-17 5:05am

Is it sorting objects on the basis of alphabetical order?

OriginalGriff 30-Apr-17 5:27am

Yes.

Thenewbieee 30-Apr-17 5:31am

How 0 and 1 works? Can you please explain that?

Thenewbieee 30-Apr-17 5:32am

Isn't is comparing just two values? what about the third value?

OriginalGriff 30-Apr-17 6:05am

What third value?
You sort by comparing values in pairs: even the simplest (bubble) sort does this by comparing two adjacent elements and swapping them if they are out of order. There is no need to compare a third value with anything.
See here, there is an animated picture which explains it:
https://en.wikipedia.org/wiki/Bubble_sort

Thenewbieee 30-Apr-17 6:11am

Okay, thanks a lot.

OriginalGriff 30-Apr-17 6:18am

You're welcome!

[no name] 30-Apr-17 10:47am

A 5 for your help