Develop Reference

IndexedDB object.put throwing ConstraintError

I have some javascript which returns an object from IndexedDB, then update some properties, and then tries to 'update' (well, add really) using put, however this throws a Constraint Error and I can't figure out why. The chunk of javascript looks like this:
indexedDbReturnRecord(AddressID, 'AddressID', 'AddressStore', function(retObject) {
retObject.DateMovedIn = getDate();
var dataToUpdate = new Array();
dataToUpdate.push(retObject);
indexedDbAddObject(dataToUpdate, 'AddressStore', function () {
noCss();
$('#CompleteBTN .ui-btn-text').text("Complete").button('refresh');
});
});

You will have to provide some more information...
What is the definition of your objectstore?
The issue will probably be something with the configuration of the key on the object store and not providing it. Is see you are trying to save an array, and in this case I think you will have to use an external key.
Another possibility is issues with indexes on the store.

Issue with retrieving object data on IE 8 on Windows XP or 2003

This is an interesting problem that I am facing with JavaScript and IE8 on Windows XP and Windows 2003. I create an object on the page and then retrive information about that object (for example, its version). When trying to get the version, I am running this code:
var myObject = document.getElementById(objectId);
console.log(myObject.version);
What is interesting is that this code works on every single browser except IE8 on Windows XP and 2003. I've done some debugging and this is where things get interesting.
myObject is not null but myObject.version is undefined. So what I did is I added an alert in between so the code is now as follows:
var myObject = document.getElementById(objectId);
alert(myObject.version);
console.log(myObject.version);
The alert results in "undefined", however, the console.log is now resulting in the actual version. If I add an alert before this alert of anything (let's say alert("something")) then the second alert has the actual version now. I am assuming this is a timing issue (for some reason the object needs sometime to be able to provide the data stored in it?) but I am not sure what kind of timing issue this is or how to approach it.
Sorry for the long description but any help is appreciated.

document.getElementById doesn't return an object. It returns a DOM element. So, you expect to see a .version property in a DOM element, which by the official W3C specification is missing (or at least I don't know about this).
I'm not sure what you are expecting to see in .version, but if it is something custom then you should create a custom object like that:
var o = { version: "..." }
console.log(o);
You said that this may be a time issue. If that's true then I'll suggest to try to access the .version property after the DOM is fully loaded. You can use jQuery for the purpose:
$(document).ready(function() {
var myObject = document.getElementById(objectId);
alert(myObject.version);
console.log(myObject.version);
});
You can add a setTimeout in your function till the .version property is there.
var f = function(callback) {
var check = function() {
var myObject = document.getElementById(objectId);
alert(myObject.version);
console.log(myObject.version);
if(typeof myObject.version !== "undefined") {
callback(myObject.version);
} else {
setTimeout(check, 1000);
}
}
setTimeout(check, 1000);
}

What happens if you put the <script>...</script> tag with the js code at the end of the html file? In my opinion, the code is executed when the DOM is not ready. If you put it in the end, then it will be executed after it's loaded.

This object constructor is preventing my script from running

I'm working on a project (creating a browser based check list). One of my goals has been to write every piece by hand without a library like jquery or a mysql database.
Currently I'm trying to create on object for managing tasks. I'm not finished the primary function, but everything is closed, and I don't detect any errors. Furthermore, I'm haven't iterated it or called it's functions yet, so there's nothing to reference it yet. When I comment it out, the script runs normally.
I've included the xml request links up above and tested them successfully in a separate portion of the script.
I'm testing in firefox.
I'm writing this in SciTE
Here's the code:
function Task(name,node,childNode,divClass,content,onclick)
{
function retrieveTask(node,childNode)
{
var taskArray = [];
taskArray.push(xmlDoc.getElementsByTagName(name)[node].childNodes[childNode].nodeValue;)
taskArray.push(xmlDoc.getElementsByTagName(description)[node].childNodes[childNode].nodeValue;)
taskArray.push(xmlDoc.getElementsByTagName(complete)[node].childNodes[childNode].nodeValue;)
return taskArray;
}
function displayTask(name,content)
{
var task = retrieveTask(node,childNode);
var clickDiv = "";
formatDiv(name,"task",task[1],clickDiv);
task[2] === true ? formatDiv(name+1,"incompleteBox"," ",clickDiv) : formatDiv(name+1,"completeBox","O",clickDiv);
}
}
If anyone could give me some insight or tips that would be awesome. This isn't homework, it's a hobby, so it's a self teaching process.

...childNodes[childNode].nodeValue;)
should be );

Auto-load/include for JavaScript

I have file called common.js and it's included in each page of my site using <script />.
It will grow fast as my sites functionality will grow (I hope; I imagine). :)
Lets example I have a jQuery event:
$('#that').click(function() {
one_of_many_functions($(this));
}
For the moment, I have that one_of_many_functions() in common.js.
Is it somehow possible that JavaScript automatically loads file one_of_many_functions.js when such function is called, but it doesn't exist? Like auto-loader. :)
The second option I see is to do something like:
$('#that').click(function() {
include('one_of_many_functions');
one_of_many_functions($(this));
}
That not so automatically, but still - includes wanted file.
Is any of this possible? Thanks in an advice! :)

It is not possible to directly auto-load external javascripts on demand. It is, however, possible to implement a dynamic inclusion mechanism similar to the second route you mentioned.
There are some challenges though. When you "include" a new external script, you aren't going to be able to immediately use the included functionality, you'll have to wait until the script loads. This means that you'll have to fragment your code somewhat, which means that you'll have to make some decisions about what should just be included in the core vs. what can be included on demand.
You'll need to set up a central object that keeps track of which assets are already loaded. Here's a quick mockup of that:
var assets = {
assets: {},
include: function (asset_name, callback) {
if (typeof callback != 'function')
callback = function () { return false; };
if (typeof this.assets[asset_name] != 'undefined' )
return callback();
var html_doc = document.getElementsByTagName('head')[0];
var st = document.createElement('script');
st.setAttribute('language', 'javascript');
st.setAttribute('type', 'text/javascript');
st.setAttribute('src', asset_name);
st.onload = function () { assets._script_loaded(asset_name, callback); };
html_doc.appendChild(st);
},
_script_loaded: function (asset_name, callback) {
this.assets[asset_name] = true;
callback();
}
};
assets.inlude('myfile.js', function () {
/* do stuff that depends on myfile.js */
});

Sure it's possible -- but this can become painful to manage. In order to implement something like this, you're going to have to maintain an index of functions and their corresponding source file. As your project grows, this can be troublesome for a few reasons -- the 2 that stick out in my mind are:
A) You have the added responsibility of maintaining your index object/lookup mechanism so that your scripts know where to look when the function you're calling cannot be found.
B) This is one more thing that can go wrong when debugging your growing project.
I'm sure that someone else will mention this by the time I'm finished writing this, but your time would probably be better spent figuring out how to combine all of your code into a single .js file. The benefits to doing so are well-documented.

I have created something close to that a year ago. In fact, I have found this thread by search if that is something new on the field. You can see what I have created here: https://github.com/thiagomata/CanvasBox/blob/master/src/main/New.js
My project are, almost 100% OOP. So, I used this fact to focus my solution. I create this "Class" with the name "New" what is used to, first load and after instance the objects.
Here a example of someone using it:
var objSquare = New.Square(); // Square is loaded and after that instance is created
objSquare.x = objBox.width / 2;
objSquare.y = objBox.height / 2;
var objSomeExample = New.Stuff("some parameters can be sent too");
In this version I am not using some json with all js file position. The mapping is hardcore as you can see here:
New.prototype.arrMap = {
CanvasBox: "" + window.MAIN_PATH + "CanvasBox",
CanvasBoxBehavior: "" + window.MAIN_PATH + "CanvasBoxBehavior",
CanvasBoxButton: "" + window.MAIN_PATH + "CanvasBoxButton",
// (...)
};
But make this more automatic, using gulp or grunt is something what I am thinking to do, and it is not that hard.
This solution was created to be used into the project. So, the code may need some changes to be able to be used into any project. But may be a start.
Hope this helps.
As I said before, this still is a working progress. But I have created a more independent module what use gulp to keep it updated.
All the magic que be found in this links:
https://github.com/thiagomata/CanvasBox/blob/master/src/coffee/main/Instance.coffee
https://github.com/thiagomata/CanvasBox/blob/master/src/node/scripts.js
https://github.com/thiagomata/CanvasBox/blob/master/gulpfile.js
A special look should be in this lines of the Instance.coffee
###
# Create an instance of the object passing the argument
###
instaceObject = (->
ClassElement = (args) ->
window[args["0"]].apply this, args["1"]
->
ClassElement:: = (window[arguments["0"]])::
objElement = new ClassElement(arguments)
return objElement
)()
This lines allows me to initialize a instance of some object after load its file. As is used in the create method:
create:()->
#load()
return instaceObject(#packageName, arguments)

immutable chrome sqlite return objects

I am using a sqlite DB as a storage system for a webapp. I been using the objects that are returned from queries directly in application. For example:
function get_book_by_id(id,successCallback,errorCallback)
{
function _successCallback(transaction, results)
{
if(results.rows.length==0) {successCallback(null);}
else
{
book=results.rows.item(0);
successCallback(book);
}
}
db.transaction(
function (transaction) {
transaction.executeSql("SELECT id,title,content,last_read from books where id=?;",[id], _successCallback, errorCallback);
});
}
This returns me an object with the given id, all columns are provided as properties. Nice. The problem I just figured out is that all the properties of the result set object are immutable. So for example if I want to change the property 'title' it takes no effect, which in my opinion makes no sense. Example:
get_book_by_id(1,handle,error);
function handle(book)
{
//THIS DOESN'T WORK, book.title is still what it was.
book.title=book.title+"more text";
}
I of course can convert all my DB objects into mutable objects, but I rather would not do that.
Is that an expected behavior? Can I request mutable objects?
I am using google chrome 9.0 on Mac OS X.

The WebSQL spec doesn't require for the returned item to be sealed, but it's up to the implementation (the spec does require for the item to be an ordered dictionary with the properties in the same order as the columns in your query).
And no, there is no way to explicitly request a mutable object, so you'll want to do something like the convert_to_mutable() approach suggested by Stan.
BTW, assuming you're using a 3rd party library, it probably has a function for this, for example jQuery.extend() or _.extend().

Building on Stepan's answer, but for people like me that want a quick fix from SO.
You can create another basic object and copy the sqlite row properties onto it.
Something like this:
var immutable_book = results.rows.item(0);
var book = {};
for (var prop in immutable_book) {
if (immutable_book.hasOwnProperty(prop)) {
book[prop] = immutable_book[prop];
}
}
That goes in the _successCallback, and then later you can do this:
book.title=book.title+"more text"; // works now !
I came across this issue in iOS Safari, but in Chrome and Android web-kit browsers I was able to update properties of the returned row object directly.