each_with_classes handlebars helper, adds {{item_*}} properties accessible from within the block

each_with_classes.js

/**
 * adds an a bunch of item prefixed logic to the object
 *
 *     {{#each_with_classes records prefix="record"}}
 *      <li class="record_{{item_index}}{{item_position}} {{item_alt}}">{{item_index}}</li>
 *     {{/each_with_classes}}
 *
 * results in the following html
 *
 *     <li class="record_0 record_first">0</li>
 *     <li class="record_1 record_alt">1</li>
 *     <li class="record_2">2</li>
 *     <li class="record_3 record_last record_alt">3</li>
 */
Handlebars.registerHelper("each_with_classes", function(array, fn) {
	var buffer = "";

	for (var i = 0, j = array.length; i < j; i++) {
		var item = array[i];

		// position related information
		item.item_position = '';
		if (i == 0) item.item_position = ' ' + fn.hash.prefix + '-first';
		if (i == (array.length - 1)) item.item_position += ' ' + fn.hash.prefix + '-last';

		// add alt if needed
		item.item_alt = i % 2 ? fn.hash.prefix + '-alt' : '';

		// stick an index property onto the item, starting with 1, may make configurable later
		item.item_index = i;

		// show the inside of the block
		buffer += fn(item);
	}

	// return the finished buffer
	return buffer;
});