Array sort in JavaScript

var my_array = new Array('lmn','ABC', 'qwt');
my_array.sort();
for (i=0;i<my_array.length;i++)
{
document.write(my_array[i] + "<br >");
}

output

ABC
lmn
qwt

We can sort elements of an array by using sort() function in JavaScript. This sort() function once applied changes the positions of the elements and arrange them in alphabetical or increasing order. Here is the basic syntax of the sort function.

Array.sort();

By default this sort is in lexicographical order or dictionary order. Check this example and its output.

<script>
var no_array = new Array(2, 22, 4, 24, 32);
var no_array2=no_array.sort();
for (i=0;i<no_array2.length;i++)
{
document.write(no_array2[i] + "<br >");
}
</script>

Output is here

The sorting is done according to string Unicode code points.

Optional Campare function

We can define our sorting algorithm in a function and JavaScript will use the function to sort the array. Function conditions are here

The function will accept two arguments and these arguments are to be compared for the algorithm. The function will return numbers based on the comparison of the two arguments.
returned number is < 0 : The first argument should appear before the second argument.

returned number is > 0 : The first argument should appear after the second argument.

returned number is equal to 0 then both the arguments should be equal.

Let us try to sort the array elements now by using optional compare function.

<script>
function bylength(a1,a2){
if(a1 < a2)
return -1;
if(a1 > a2)
return 1;
if(a1 == a2)
return 0;
}
var no_array = new Array(2, 22, 4, 24, 32);

var no_array2=no_array.sort(bylength);
for (i=0;i<no_array2.length;i++)
{
document.write(no_array2[i] + "<br >");
}
</script>

Output is here

To change the order to descending, we must change the comparison inside the function or change this line ( swap a1,a2 ).

function bylength(a2,a1){

Sorting elements in ascending and descending order with sample code.
Now let us try to create an array and then display them to see the elements and their order. After this we will apply sort() function and then again we will display the elements of the array to check the order.
Demo of displaying in alphabetical order
Here is the code.

<script language="javascript">
var scripts = new Array();
scripts[0] = "PHP";
scripts[1] = "ASP";
scripts[2] = "JavaScript";
scripts[3] = "HTML";
for (i=0;i<scripts.length;i++)
{
document.write(scripts[i] + "<br >");
}

scripts=scripts.sort();
document.write("<br>--Now after the sort---<br>");
for (i=0;i<scripts.length;i++)
{
document.write(scripts[i] + "<br >");
}
</script>

In the order of length of the element

Demo of displaying in the order of length
Here is the code.

<script language="javascript">
function bylength(a1,a2){
if(a1.length < a2.length)
return -1;
if(a1.length > a2.length)
return 1;
if(a1.length == a2.length)
return 0;

}
var scripts = new Array();
scripts[0] = "PHP";
scripts[1] = "ASP";
scripts[2] = "JavaScript";
scripts[3] = "HTML";
for (i=0;i<scripts.length;i++)
{
document.write(scripts[i] + "<br >");
}
document.write("<br>-----<br>");

scripts=scripts.sort(bylength);q
for (i=0;i<scripts.length;i++)
{
document.write(scripts[i] + "<br >");
}
</script>

Output is here

PHP
ASP
JavaScript
HTML

--After the sort()---

PHP
ASP
HTML
JavaScript

Reversing the order of the elements of an Array
Array Reference How to display elements of an Array

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Sorting of array in JavaScript

Optional Campare function

In the order of length of the element

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