The handlers of the product amount field were implemented.

sales/static/js/app.js

@@ -0,0 +1,28 @@
+$(document).ready(function() {
+
+	var $amount_field = $('#amount');
+
+	$('#add_product').on('click', function() {
+
+		var value = to_int($amount_field)
+		$amount_field.val(value + 1)
+
+		//TODO: No exceder la cantidad máxima de producto
+
+	})
+
+	$('#remove_product').on('click', function() {
+
+		var value = to_int($amount_field) - 1
+		$amount_field.val(value < 0 ? 0 : value)
+
+	})
+})
+
+function to_int($element) {
+	var value = $element.val()
+	value = value == '' ? 0 : parseInt(value)
+	return value
+}
+
+