There are 2 previous versions of this script.
// ==UserScript==
// @name Tesco Money Saver
// @namespace TescoMoneySaver
// @description Browse groceries by price, enabling you to choose value-for-money over the best-known brand.
// @include http://www.tesco.com/superstore/product/shelf.aspx?*
// ==/UserScript==
//////main code/////
//if product list exists, continue
if (productsNode = document.getElementById("products")) {
//create input (i.e. original products in original order) items list
var inputList = new Array();
//create output list
var outputList;
//populate input list
for (i = 0; i < countProducts(); i++) {
inputList[i] = getProduct(i);
}
//if sort by price is turned on, continue
if (document.cookie.match("sortByPrice=true")) {
// add ticked checkbox to page
addCheckbox(productsNode, true);
sortByPrice();
printSorted();
}
//if sorting by price is disabled
else {
//... add unticked checkbox to page
addCheckbox(productsNode, false);
}
}
//////functions//////
/////// object product constructor////
function product(id, rank) {
this.id = id; //- tesco's id for item
this.price = eval(document.getElementById("" + id + "-p").innerHTML); //- price in pounds
this.html = getHTMLbyID(id); // - original html code for this item to make the item appear on the page
this.next = null; //- next node in linked list
this.previous = null; //- previous node in linked list
this.rank = rank; //- original ranking on page (alphabetically) so can be reverted later if desired
}
////// object linkedList constructor ///////
function linkedList(){
this.firstNode = null;
this.lastNode = null;
}
// count number of products on page
function countProducts() {
var count = 0;
productList = document.getElementById("products");
return productList.childNodes.length;
}
// return a product by place in original list
function getProduct(index) {
productList = document.getElementById("products");
if (productList){
productId = productList.childNodes.item(index).firstChild.id;
return new product(productId, index);
}
else {alert("error: Product list not found. Please report how this happened so this problem can be eliminated.");}
}
// get html of item by id
function getHTMLbyID(myID){
myElement = document.getElementById(myID);
if (myElement) {
return myElement.innerHTML;
}
}
// set html of item by id
function setHTMLbyID(myHTML, myID){
myElement = document.getElementById(myID);
if (myElement) {
myElement.innerHTML = myHTML;
}
}
// insert a new node after an existing node
function insertAfter( list, node, newNode) {
newNode.previous = node;
newNode.next = node.next;
if (node.next == null) {
node.next = newNode;
list.lastNode = newNode;
}
else {
node.next.previous = newNode;
node.next = newNode;
}
}
// insert a new node before an existing node
function insertBefore(list, node, newNode) {
newNode.previous = node.previous;
newNode.next = node;
if (node.previous == null) {
node.previous = newNode;
list.firstNode = newNode;
}
else {
node.previous.next = newNode;
node.previous = newNode;
}
}
// insert a node at the beginning of the list
function insertBeginning(list, newNode) {
if (list.firstNode == null) {
list.firstNode = newNode;
list.lastNode = newNode;
newNode.prev = null;
newNode.next = null;
}
else {
insertBefore(list, list.firstNode, newNode)
}
}
// insert a node at the end of the list
function insertEnd(list, newNode) {
if (list.lastNode == null) {
insertBeginning(list, newNode);
}
else {
insertAfter(list, list.lastNode, newNode);
}
}
// switch price sorting from current setting (i.e. on -> off or off -> on)
function switchPriceSort() {
//if sorting is enabled...
if (document.cookie.match("sortByPrice=true")) {
//...turn it off
document.cookie="sortByPrice=false; path=/";
//and revert sorting to original order
revertSorting();
}
// sorting disabled...
else {
//.... turn it on!
document.cookie="sortByPrice=true; path=/";
// and then carry out sorting
if (outputList == null) {
sortByPrice();
}
printSorted();
}
}
//set an attribute for a node
function setMyAttribute(node, attName, attValue) {
att = document.createAttribute(attName);
att.value = attValue;
node.setAttributeNode(att);
}
//check url's terms for a match to provided string
function urlContains(str){
return location.search.match(str);
}
//creates a checkbox which can enable or disable sorting by price
function addCheckbox(node, checked) {
// create div node
divNode = document.createElement('DIV');
// create div's children, input and label
inputNode = document.createElement('INPUT');
labelNode = document.createElement('LABEL');
//set labelNode attribute for => sortByPriceBox
setMyAttribute (labelNode, "for", "sortByPriceBox");
//set inputNode's attibutes - type => checkbox, checked => checked, onclick => switchPriceSort(this), name => sortByPriceBox
setMyAttribute(inputNode, "type", "checkbox");
if (checked) {
setMyAttribute(inputNode, "checked", "checked");
}
inputNode.addEventListener("click", switchPriceSort, true);
setMyAttribute(inputNode, "name", "sortByPriceBox");
//append label text to labelNode
textNode = document.createTextNode("Show products cheapest first");
labelNode.appendChild(textNode);
//add style attributes to checkbox to match current "show images" checkbox as of 17/2/08
setMyAttribute(divNode, "style", "font-size:0.7em; margin: 0em 1.4em 0 1.3em; width:50%; font-weight:bold");
setMyAttribute(inputNode, "style", "border: 0px solid white; margin: 0 0.5em 0 0; padding:0");
setMyAttribute(labelNode, "style", "padding-left:0.2em; color:#333333");
// append input and label to div
divNode.appendChild(inputNode);
divNode.appendChild(labelNode);
//insert into DOM
node.parentNode.insertBefore(divNode, node);
}
// traverse an output list to find item specified by rank
function getProductByRank(outlist, rank) {
examinedItem = outlist.firstNode;
if (examinedItem.rank == rank) {
return examinedItem;
}
while (examinedItem.next) {
if (examinedItem.next.rank == rank) {
return examinedItem.next;
}
examinedItem = examinedItem.next
}
}
// revert sorted page to unsorted page
function revertSorting () {
for (i = 0; i < inputList.length; i++) {
setHTMLbyID(inputList[i].html, getProductByRank(outputList, i).id);
}
}
// traverse sorted output list and print in order
function printSorted() {
//for each product on page
examinedItem = outputList.firstNode;
setHTMLbyID(getHTMLbyID(examinedItem.id), inputList[0].id);
for (i = 1; i < countProducts(); i++) {
//replace with outputList item
setHTMLbyID(examinedItem.next.html, inputList[i].id);
if (examinedItem.next) {examinedItem = examinedItem.next;}
}
}
// set global variable outputList to a linked list of products ordered in ascending order (cheapest first)
function sortByPrice() {
// create list for outputting
outputList = new linkedList();
//add first item to output list
insertBeginning(outputList, inputList[0]);
//if second item is cheaper, add to beginning...
if (inputList[1].price < inputList[0].price) insertBeginning(outputList, inputList[1]);
//...or else add to the end
else insertEnd(outputList, inputList[1]);
/////add products to output list///////
//get a new product to enter to the output list
for (i = 2; i < inputList.length; i++) {
newProduct = inputList[i];
//create an iteration pointer to traverse the list
examinedProduct = outputList.firstNode;
// look through output list until a place is found for the new product
flagItemNotPlacedYet = true;
while (flagItemNotPlacedYet) {
//if new product is cheaper than examined product...
if (newProduct.price < examinedProduct.price) {
//... then add new product before examined product in the list
insertBefore(outputList, examinedProduct, newProduct);
//mark it as placed
flagItemNotPlacedYet = false;
}
else if (examinedProduct.next == null) {
//...add new product to end of list
insertEnd(outputList, newProduct);
//and mark item as placed
flagItemNotPlacedYet = false;
}
//if more products left to examine...
if (examinedProduct.next != null) {
// examine next product
examinedProduct = examinedProduct.next;
}
}
}
}
