Simple textarea diff functionality.

textareadiff.js

/*
 * Textarea Diff
 * Simple textarea diff functionality.
 *
 * Copyright 2010, Nathan Hammond
 * Released under the MIT License
 */

function diff(oldtext, newtext) {
	// Only one difference. Guaranteed contiguous.
	// Protect the special case of inserting or deleting an adjacent repeating token.

	for (var beginning = 0; oldtext[beginning] === newtext[beginning]; beginning++) {}
	var endmax = Math.max(newtext.length - beginning, oldtext.length - beginning);
	for (var end = 0; oldtext[oldtext.length-end] === newtext[newtext.length-end], end < endmax; end++) {}
	var content = newtext.substring(beginning, (newtext.length-end+1));

	return { beginning: beginning, end: end, content: content};
}