I am new to programming and javascript and i have a question ive been struggling with for a bit now. Im trying to build a card game and have a card object which returns a card representation of the format (card #,suit eg. 5,Hearts). I deal a card at the start of the program and validate that the card dealt is unique (ie not been used already). I have the following structure:
var usedCards= [];
function dealCards() {
for (i = 0; i < 3; i++)
{
var card = createUniqueCard();
usedCards.push(card.cardRepresentation);
}
}
function createUniqueCard() {
do {
var newCard = new Card();
}
while (usedCards.indexOf(newCard.cardRepresentation) != -1);
return newCard;
}
This still returns me duplicate cards in my usedCards array. Can anyone point out my logic error?
Thanks
If newCard.cardRepresentation is an object then .indexOf() will never find a match because two object references are considered equal only if they refer to the same instance - you keep creating new instances with new Card().
If you can have newCard.cardRepresentation as a string it should work. Or if you write your own function to replace .indexOf(), where your function knows how to compare two .cardRepresentation objects...
I think a better solution is to begin by generating all possible cards, putting them in an array, and then your deal function could randomly select from that array.
Related
This question already has answers here:
Length of a JavaScript object
(43 answers)
Closed 2 years ago.
Lately I have been trying to create a webpage with a search feature. My way of implementing this, while not the fastest or most elegant, should work in theory. All it does is split the search term into a list, the delimiter being a space, and then splits the keywords (in dictionary format, with the value being a download link, and with the key being the "keywords" I was referring to) and finally, it has an outer loop looping through the keys (being split each iteration into a list), and an inner loop looping through the words input through the input field. If a word in the search field matches one keyword of the key words list, then that key from the dictionary gets a score of +1.
This should sort the keys into order of best result to worst, and then the code can continue on to process all this information and display links to the downloadable files (the point of the webpage is to supply downloads to old software [of which I have collected over the years] etc.). However, when I run the program, whenever the alert(ranking.length) function is called, all I get is undefined in the output window.
Here is the code. (The search() function is called whenever the search button is pressed):
var kw_href = {
"windows":["windows3.1.7z"],
"ms dos 6.22":["ms-dos 6.22.7z"]
}
function search(){
var element = document.getElementById("search_area");
var search_term = element.value.toLowerCase();
var s_tags = search_term.split(" ");
var keys = Object.keys(kw_href);
ranking = {
"windows":0,
"ms dos 6.22":0
};
for (i = 0; i < keys.length; i++){
keywords_arr = keys[i].split(" ");
for (x = 0; x < s_tags.length; x++){
if (keywords_arr.includes(s_tags[x])){
ranking[keys[i]] = ranking[keys[i]] + 1;
}
}
}
// now we have a results list with the best results. Lets sort them into order.
alert(ranking.length);
}
Edit
alert(ranking.length) line is for debugging purposes only, and I was not specifically trying to find the length.
ranking is a generic object, not an array, so it won't have a computed length property.
If you want to count the number of properties in it, convert it to an array with Object.keys(ranking).
ranking should be array of object like ranking =[{"windows":0,"ms dos 6.22":0},{"windows":1,"ms dos 6.22":10}]
Then length ranking.length will work
I'm trying to clear all local storage when the user either completes the game loop or starts a new game, but also keep some values.
I can do this already with my sound values for volume:
// inside a conditional statement that fires when the user chooses to start a new game.
if (newGameBool === '1') {
var tst = myAu;
//myAu is the stored value that the user sets as sound using a range type input
localStorage.clear();
localStorage.setItem("Au", tst);//A newly cleared localStorage just got a new value, and it's the same as it was before.
UI.myLoad();//reload the function that uses LS to do things.
}
How do I do this for key's that have an iterating number attached to them?
Here is how I save them:
var i = +v + +1;
localStorage.setItem("v", i);
var vv = localStorage.getItem("v");
localStorage.setItem("LdrBrd_" + vv, JSON.stringify(LdrBrd));//saves all data with the iterating key name.
Calling them the way i did the sound function:
var gv = v + 1;//v calls the value from LS and adjusted for off-by-one error. gv is a local variable.
if (newGameBool === '1') {
var ldd, vg;
for (var ii = 0; ii < gv; ii++) {
var ld = localStorage.getItem("LdrBrd_" + ii);
if (ld != null) {
//these are the values that i want to pass beyond the clear point
ldd = JSON.parse(ld);//JSON string of data saved
vg = ii;//how many of them.
}
}
localStorage.clear();
for (var xx = 0; xx < vg; xx++) {
var nld = localStorage.getItem("LdrBrd_" + xx);
if (nld != null) {
localStorage.setItem("LdrBrd_" + ii, JSON.stringify(ldd));
}
}
localStorage.setItem("v", vg);
UI.myLoad();
}
I have been using console.log() in various spots to see what is going on. I comment-out the clear function just to see if the values were wrong and they don't save all all. I tried to make a fiddle, but the local storage wasn't working at all there. In visual studio, it works fine but the script to this file is almost 2000 lines long, so i tried to dress it up the best i knew how.
Thanks in advance for any help or guidance.
I was stuck on this for a few days, but i think i found something that will work, so i'll answer my own question in case there is value in posterity.
locatStorage.clear();
/* ^LS clear() function is above all new setItem codes, some variables are declared globally and some are declared at the top of the functional scope or as param^ */
var itemClass = document.querySelectorAll(".itemClass");//the strings are here
if (itemClass) {//make sure some exist
for (var p = 0; p < itemClass.length; p++) {//count them
mdd = JSON.parse(itemClass[p].innerText);//parse the data for saving
localStorage.setItem("v", v);//this is the LS item that saves the amount of items i have, it's declared at the top of the functions timeline.
localStorage.setItem("LdrBrd_" + p, JSON.stringify(mdd));//this setItem function will repeat and increment with 'p' and assign the right string back to the key name it had before.
}
}
The key is to keep the strings physically attached to an element, then call the class name. The i ran a loop counting them. 'mdd' will spit back each item i want. So then all that is left to do is re-set the item back to it's original status.
This has allowed me to create a way for my users to collect trophies and keep them even after clearing the localStorage when the he/she decides to start a new game.
I use CSS to hide the text from the string.
color:transparent;
In my gameLoop, i have a function that will read the saved strings and show them as cards just below the hidden strings.
Since you want to keep some values I recommend one of two things:
Don't call localStorage.clear() and instead only wipe out the values that you want using localStorage.removeItem('itemName'). Since you said the item names have a numeric component, maybe you can do this in a loop to reduce code.
Pull item(s) that you want saved first and restore them after calling clear(). This option is best if there are way more items that you want removed rather than saved (see below)
function mostlyClear() {
var saveMe = {};
saveMe['value1'] = localStorage.getItem('value1');
saveMe['anotherValue'] = localStorage.getItem('anotherValue');
localStorage.clear();
for(var prop in saveMe) {
if(!saveMe.hasOwnProperty(prop)) continue;
localStorage.setItem(prop, saveMe[prop]);
}
}
I know there are several issues with JavaScript Array.push() method posted here, but I can't get the following example to work:
First of all, i got a global Array:
var results = new Array();
for (var i = 0; i < X.length; i++) {
results[i] = new Array();
}
Now this array should be filled on a button-event. All I want is to fill the Array with new Arrays and push some data to them. The following code should check if results[x][y] already is an Array (and create one if it's not) and push data to it.
So, in the end, there should be an Array (result) that contains X.length Arrays filled with an unknown number of new Arrays, each of them containing an unknown number of data:
function pushResult(result) {
if (typeof results[currentStim][currentDist] == 'undefined') {
results[currentStim][currentDist] = new Array();
}
results[currentStim][currentDist].push(result);
}
Problem is: It just doesn't work. I made sure that currentStim is never out of bounds, I made sure that the "if"-Statement is only accessed when needed (so the Array isn't overwritten with a new one) and I watched the return-value of push(), always throwring back a number representing the new array length. As expected, this number increases evertime a value is pushed to an Array.
However, when I finally call:
document.getElementById('results').value = JSON.stringify(results);
to pass results to my PHP-script, something like this will be passed:
[[],[[1]],[],[]]
push()was called MUCH more often than once (at least "1" is one of the results I wanted to be stored) and, as described, always returned an increasing arrayLength. How does that work? What happened to my data?
I testet this on Chrome as well as on Firefox, same result. It might be interesting that a seperate loop draws to a Canvas the same time, but that shouldn't interupt Array-Handling and onKey-Events, right?
Hope u can help me,
MA3o
EDIT:
pushResult is called like this:
// Handles Space-Events
function pushed(event) {
if (event.which == 32 && stimAlive) {
pushResult(1);
hitCurrent = true;
}
Where hitCurrent and stimAlive are just flags set somewhere else. Some code further the function pushedis registered as an event listener:
document.onkeydown = function(event) { pushed(event)}
All the functions are called correctly. Adding console.log(results) to every loop just shows the right Array, as far as I can see.
According to the comments, the problem might be that "currentDist" can be a float value.
Alright, so the thing is;
Now I made this website for myself to study japanese more easily, by making a list of japanese words and its definition. I put the japanese words in lesson1.txt and the answers in lesson1answers.txt in the same order. I read them out in php and put them in arrays in javascript.
Now the problem is is that these arrays have the same order every time I start the site, which is quite annoying for me as I keep resembling the spot to the answer, and I dont even read the japanese word (Damn our human brains!). So I figured the best way to solve this is by randomizing the elements of both the arrays, but they both have to be randomized in the same pattern because else the question doesnt correspond correctly to the answer anymore.
One of the arrays I have is multidimensional. The array first holds elements that represent the lines I read out of a .txt file. The line has multiple characters in it, consequently the second element of the array represents each character (Dont ask me why I did this, it had to do with me not being able to read out japanese characters in php and put them in js directly). The other array is just the array I keep the answers in.
So I have AnswersArray(); and JapaneseCharactersArray();
I've been stuck on this problem for a whole day now, someone please help or give a hint..
You should merge them into one array of objects:
// assuming AnswersArray.length == JapaneseCharactersArray.length
var array = [];
for (var i=0; i<AnswersArray.length; i++)
array[i] = {
answer: AnswersArray[i],
japanese: JapaneseCharactersArray[i]
};
Now you have only one array, each item containing all information on a single word. You can easily shuffle it now.
Instead of AnswersArray[x] you then would use array[x].answer further down in your code.
Of course, you could just adapt your fisherYates function to shuffle two or more arrays in the same way:
function fisherYates(first/*, ... arrays */) {
var i = first.length,
argl = arguments.length;
if (i == 0) return false;
while (--i) {
var r = Math.floor(Math.random() * (i + 1));
for (var j=0; j<argl; j++) {
var tempi = arguments[j][i];
var tempj = arguments[j][r];
arguments[j][i] = tempj;
arguments[j][r] = tempi;
}
}
}
// usage:
> fisherYates(AnswersArray, JapaneseCharactersArray);
Although the best way is probably to just create them as a single array, another way is to create a new array, of the same length as the others, where each item in the array is a number: 1, 2, 3 ... n. But instead of having the numbers in order, use Math.random() to randomize their order.
Then loop through that new array as such:
for(i=0; i<AnswersArray.length; i++) {
AnswersArray[RandomArray[i]]; // whatever
}
Another way is to just swap the entire row when you randomize the array.
How do I remove an items from a data bound array? My code follows.
for(var i = 0; i < listBox.selectedIndices.length; i++) {
var toRemove = listFiles.selectedIndices[i];
dataArray.splice(toRemove, 1);
}
Thanks in advance!
Edit Here is my swf. The Add Photos works except when you remove items.
http://www.3rdshooter.com/Content/Flash/PhotoUploader.html
Add 3 photos different.
Remove 2nd photo.
Add a different photo.
SWF adds the 2nd photo to the end.
Any ideas on why it would be doing this?
Edit 2 Here is my code
private function OnSelectFileRefList(e:Event):void
{
Alert.show('addstart:' + arrayQueue.length);
for each (var f:FileReference in fileRefList.fileList)
{
var lid:ListItemData = new ListItemData();
lid.fileRef = f;
arrayQueue[arrayQueue.length]=lid;
}
Alert.show('addcomplete:' + arrayQueue.length);
listFiles.executeBindings();
Alert.show(ListItemData(arrayQueue[arrayQueue.length-1]).fileRef.name);
PushStatus('Added ' + fileRefList.fileList.length.toString() + ' photo(s) to queue!');
fileRefList.fileList.length = 0;
buttonUpload.enabled = (arrayQueue.length > 0);
}
private function OnButtonRemoveClicked(e:Event):void
{
for(var i:Number = 0; i < listFiles.selectedIndices.length; i++) {
var toRemove:Number = listFiles.selectedIndices[i];
//Alert.show(toRemove.toString());
arrayQueue.splice(toRemove, 1);
}
listFiles.executeBindings();
Alert.show('removecomplete:' + arrayQueue.length);
PushStatus('Removed photos from queue.');
buttonRemove.enabled = (listFiles.selectedItems.length > 0);
buttonUpload.enabled = (arrayQueue.length > 0);
}
It would definitely be helpful to know two things:
Which version of ActionScript are you targeting?
Judging from the behavior of your application, the error isn't occurring when the user removes an item from the list of files to upload. Looks more like an issue with your logic when a user adds a new item to the list. Any chance you could post that code as well?
UPDATE:
Instead of: arrayQueue[arrayQueue.length]=lid
Try: arrayQueue.push(lid)
That will add a new item to the end of the array and push the item in to that spot.
UPDATE 2:
Ok, did a little more digging. Turns out that the fileList doesn't get cleared every time the dialog is opened (if you're not creating a new instance of the FileReferenceList each time the user selects new files). You need to call splice() on the fileList after you add each file to your Array.
Try something like this in your AddFile() method...
for(var j:int=0; j < fileRefList.fileList.length; j++)
{
arrayQueue.push(fileRefList.fileList[j]);
fileRefList.fileList.splice(j, 1);
}
That will keep the fileList up to date rather than holding on to previous selections.
I see one issue. The selected indices are no longer valid once you have spliced out the first element from the array. But that should only be a problem when removing multiple items at once.
I think we need to see more code about how you are handling the upload before we can figure out what is going on. It looks to me like you are holding a reference to the removed FileReference or something. The described problem is occurring when you upload a new file, not when you remove the selected one.
Do you mean to use listBox and listFiles to refer to the same thing?
I'm stepping out on a limb here, because I don't have a ton of experience with JavaScript, but I'd do this the same way that I'd do it in C, C++, or Java: By copying the remaining array elements down into their new locations.
Assuming that listFiles.selectedIndices is sorted (and its contents are valid indices for dataArray), the code would be something like the following:
(WARNING: untested code follows.)
// Don't bother copying any elements below the first selected element.
var writeIndex = listFiles.selectedIndices[0];
var readIndex = listFiles.selectedIndices[0] + 1;
var selectionIndex = 1;
while(writeIndex < (dataArray.length - listFiles.selectedIndices.length)) {
if (selectionIndex < listFiles.selectedIndices.length) {
// If the read pointer is currently at a selected element,
// then bump it up until it's past selected range.
while(selectionIndex < listFiles.selectedIndices.length &&
readIndex == listFiles.selectedIndices[selectionIndex]) {
selectionIndex++;
readIndex++;
}
}
dataArray[writeIndex++] = dataArray[readIndex++];
}
// Remove the tail of the dataArray
if (writeIndex < dataArray.length) {
dataArray.splice(writeIndex, dataArray.length - writeIndex);
}
EDIT 2009/04/04: Your Remove algorithm still suffers from the flaw that as you remove items in listFiles.selectedIndices, you break the correspondence between the indices in arrayQueue and those in listFiles.selectedIndices.
To see this, try adding 3 files, then doing "Select All" and then hit Remove. It will start by removing the 1st file in the list (index 0). Now what had been the 2nd and 3rd files in the list are at indices 0 and 1. The next value taken from listFiles.selectedIndices is 1 -- but now, what had been the 3rd file is at index 1. So the former File #3 gets spliced out of the array, leaving the former 2nd file un-removed and at index 0. (Using more files, you'll see that this implementation only removes every other file in the array.)
This is why my JavaScript code (above) uses a readIndex and a writeIndex to copy the entries in the array, skipping the readIndex over the indices that are to be deleted. This algorithm avoids the problem of losing correspondence between the array indices. (It does need to be coded carefully to guard against various edge conditions.) I tried some JavaScript code similar to what I wrote above; it worked for me.
I suspect that the problem in your original test case (removing the 2nd file, then adding another) is analogous. Since you've only shown part of your code, I can't tell whether the array indices and the data in listFiles.selectedIndices, arrayQueue, and fileRefList.fileList are always going to match up appropriately. (But I suspect that the problem is that they don't.)
BTW, even if you fix the problem with using splice() by adjusting the array index values appropriately, it's still an O(N2) algorithm in the general case. The array copy algorithm is O(N).
I'd really need to see the whole class to provide a difinitive answer, but I would write a method to handle removing multiple objects from the dataProvider and perhaps assigning a new array as the dataProvider for the list instead of toying with binding and using the same list for the duration. Like I said, this is probably inefficient, and would require a look at the context of the question, but that is what I would do 9unless you have a big need for binding in this circumstance)
/**
* Returns a new Array with the selected objects removed
*/
private function removeSelected(selectedItems:Array):Array
{
var returnArray:Array = []
for each(var object:Object in this.arrayQueue)
{
if( selectedItems.indexOf(object)==-1 )
returnArray.push( object )
}
return returnArray;
}
You might be interested in this blog entry about the fact that robust iterators are missing in the Java language.
The programming language, you mentioned Javascript, is not the issue, it's the concept of robust iterators that I wanted to point out (the paper actually is about C++ as the programming language).
The [research document]() about providing robust iterators for the ET++ C++ framework may still e helpful in solving your problem. I am sure the document can provide you with the necessary ideas how to approach your problem.