Javascript str_replace function!

str_replace.js

function str_replace(haystack, needle, replace) {
	var haystack_arr 	= haystack.split('');
	var needle_arr 		= needle.split('');
	var replace_arr 	= replace.split('');
	var replace_positions = new Array();
	$.each(haystack_arr, function(key, value) {
		if(value == needle_arr[0]) {
			var correct_count = 1;
			for(i = 1; i < needle_arr.length; i++) {
				if(haystack_arr[key + i] == needle_arr[i]) {
					correct_count++;
				} else {
					break;
				}
			}
			if(correct_count == needle_arr.length) {
				replace_positions.push(key);
			}
		}
	});
	$.each(replace_positions, function(key, value) {
		value = value - ((needle_arr.length - 1) * key);
		haystack_arr.splice((value + 1), (needle_arr.length - 1));
		haystack_arr[value] = replace;
	});
	return haystack_arr.join('');
}

str_replace.md

I haven't really bothered refactoring it (although I'm not sure it's possible to get it any smaller) and it does rely on jQuery (if only to make my life a tiny bit easier, it would still work without with minor changes!).

Right! There's 4 files.

• str_replace.js: This is the function without any blank lines or comments.

• str_replace_cleaner.js: Same as above with blank lines and comments.

• str_replace_prototype: Same as above but it modifies the strings prototype so you can call the function the same way you'd call .replace()

• str_replace.php The same challenge in PHP.

Pretty fucking nifty huh?

str_replace.php

<?php

	class String {

		// Public vars.
		public $string;

		// Private vars.
		private $needle_arr, $replace_arr, $haystack_arr, $replace_positions;

		// Construct.
		public function __construct($string) {
			$this->string = $string;
		}

		// Replace function.
		public function replace($needle, $replace) {
			$this->haystack_arr = str_split($this->string);
			$this->needle_arr = str_split($needle);
			$this->replace_arr = str_split($replace);
			$this->replace_positions = array();
			
			foreach($this->haystack_arr as $key => $value) {
				if($value == $this->needle_arr[0]) {
					$correct_count = 1;

					for($i = 1; $i < count($this->needle_arr); $i++) {
						if($this->haystack_arr[$key + $i] == $this->needle_arr[$i]) {
							$correct_count++;
						} else {
							break;
						}
					}

					if($correct_count == count($this->needle_arr)) {
						$replace_positions[] = $key;
					}
				}
			}

			foreach($replace_positions as $key => $value) {

				$value = $value - ((count($this->needle_arr) -1) * $key);

				array_splice($this->haystack_arr, $value, count($this->needle_arr), $replace);

			}

			$this->string = implode($this->haystack_arr, '');
			return $this->string;
		}

	}


	// Demo.
	$string = new String('Hello. Hello. Hello.');
	$string->replace('Hello', 'Goodbye');

	echo $string->string;
?>

str_replace_cleaner.js

$(document).ready(function() {
	str_replace('The rabbit is awesome, I mean who wouldnt love rabbits?', 'rabbit', 'fox');
});

function str_replace(haystack, needle, replace) {
	// Split all the strings into arrays.
	var haystack_arr 	= haystack.split('');
	var needle_arr 		= needle.split('');
	var replace_arr 	= replace.split('');

	// Find the length of the needle array.
	var replace_positions = new Array();

	// Loop through each character of the haystack.
	$.each(haystack_arr, function(key, value) {

		// Check if this character matches the first of our needle.
		if(value == needle_arr[0]) {
			var correct_count = 1;

			// Go through the next few letters to check if the full phrase is there.
			for(i = 1; i < needle_arr.length; i++) {
				if(haystack_arr[key + i] == needle_arr[i]) {
					correct_count++;
				} else {
					break;
				}
			}

			// Check if the correct count is the same as the needle length.
			if(correct_count == needle_arr.length) {
				replace_positions.push(key);
			}
		}
	});

	// Loop through the positions and replace all the letters!
	$.each(replace_positions, function(key, value) {

		// Calculate the offset based on previous replacements.
		value = value - ((needle_arr.length - 1) * key);

		haystack_arr.splice((value + 1), (needle_arr.length - 1));
		haystack_arr[value] = replace;
	});

	return haystack_arr.join('');
}

str_replace_prototype.js

$(document).ready(function() {
	var test = 'The rabbit is awesome, I mean who wouldnt love rabbits?';
	alert(test.joey_replace('rabbit', 'fox'));
});

String.prototype.joey_replace = function(needle, replace) {
	// Split all the strings into arrays.
	var haystack_arr 	= this.split('');
	var needle_arr 		= needle.split('');
	var replace_arr 	= replace.split('');

	// Find the length of the needle array.
	var replace_positions = new Array();

	// Loop through each character of the haystack.
	$.each(haystack_arr, function(key, value) {

		// Check if this character matches the first of our needle.
		if(value == needle_arr[0]) {
			var correct_count = 1;

			// Go through the next few letters to check if the full phrase is there.
			for(i = 1; i < needle_arr.length; i++) {
				if(haystack_arr[key + i] == needle_arr[i]) {
					correct_count++;
				} else {
					break;
				}
			}

			// Check if the correct count is the same as the needle length.
			if(correct_count == needle_arr.length) {
				replace_positions.push(key);
			}
		}
	});

	// Loop through the positions and replace all the letters!
	$.each(replace_positions, function(key, value) {

		// Calculate the offset based on previous replacements.
		value = value - ((needle_arr.length - 1) * key);

		haystack_arr.splice((value + 1), (needle_arr.length - 1));
		haystack_arr[value] = replace;
	});

	return haystack_arr.join('');
}