# Friday Algorithms: Quicksort – Difference Between PHP and JavaScript

Here’s some Friday fun. Let me show you one sorting algorithm, perhaps the most known of all them – the quick sort, implemented both on PHP and JavaScript. Although the code look similar between both languages, there are few differences, that show the importance of the syntax knowledge!

### 1. PHP

```<?php   \$unsorted = array(2,4,5,63,4,5,63,2,4,43);   function quicksort(\$array) { if (count(\$array) == 0) return array();   \$pivot = \$array; \$left = \$right = array();   for (\$i = 1; \$i < count(\$array); \$i++) { if (\$array[\$i] < \$pivot) \$left[] = \$array[\$i]; else \$right[] = \$array[\$i]; }   return array_merge(quicksort(\$left), array(\$pivot), quicksort(\$right)); }   \$sorted = quicksort(\$unsorted);   print_r(\$sorted);```

### 2. JavaScript

```var a = [2,4,5,63,4,5,63,2,4,43];   function quicksort(arr) { if (arr.length == 0) return [];   var left = new Array(); var right = new Array(); var pivot = arr;   for (var i = 1; i < arr.length; i++) { if (arr[i] < pivot) { left.push(arr[i]); } else { right.push(arr[i]); } }   return quicksort(left).concat(pivot, quicksort(right)); }   console.log(quicksort(a));```

Note that the first conditional statement is quite important! While in PHP the count function will return 0 either on a NULL value or an empty array and you can substitute it with something like count(\$array) < 2

```if (count(\$array) < 2) return \$array;```

in JavaScript you cannot use that because of the presence of the ‘undefined’ value when an “empty” array is passed as an argument. Thus you’ve the conditional above:

```// this will result with an error if (arr.length < 2) return arr;```

## Coming Up Next …

An iterative version of the algorithm next Friday!

## 6 thoughts on “Friday Algorithms: Quicksort – Difference Between PHP and JavaScript”

1. Filip says:

Hi, I have to make javascript quick sort animation but I have some troubles. Please… don’t you know, how to make it possible? Because of undefined statement I’m quite disoriented.

2. Stoimen says:

@Filip – please provide some code as an example!

3. Filip says:

http://pastebin.com/UFaT4r4C (val[] is array)

I need quick sort that doesn’t work with buffers, like you did. Just let it work on one array, because I want to animate it and each swap save in another array to use it on animating etc… This algorithm works with PHP, C++, but with this implementation, it doesn’t work. In while loops I get into undefined statement and whole algorithm loops forever.

4. Filip says:

I did mistake. =) I meant, that this implementation works with PHP, C++, Pascal but with javascript it doesn’t work, because of undefined statement. There are lots of implementation, but no one is suited for animation that I need to school project.

Thank you very much! =)

5. tzulac says:

I started to study algorithm (and started with sorting algorithms of course!) and found some interesting thing. I looked on the web for examples and all use at iteration something like that (and you too):
for (\$i = 1; \$i < count(\$array); \$i++)…
I found that is not efficient as time consuption because array elements must be counted at every iteration. I think is optim to memorize counted value first. I run some test and found that.
6. Stoimen says: