Develop Reference

How to select the first element of an object in javascript on IE8 without using []?

I'm fighting with IE8 and the flashcanvas.js plugin trying to capture a signature.
The demo works fine on IE8, but since I'm using a bunch of other plugins including requireJS, I'm running into some kind of problem on IE8.
I have nailed it down to this:
function onReadyStateChange() {
if (document.readyState === "complete") {
document.detachEvent(ON_READY_STATE_CHANGE, onReadyStateChange);
var canvases = document.getElementsByTagName(CANVAS);
// => returns 1 in IE8 debugger
console.log( canvases.length )
// => returns objectHTMLCollection
console.log( canvases )
for (var i = 0, n = canvases.length; i < n; ++i) {
console.log(" run "+i)
// => this produces an error...
console.log( canvases[i])
// trigger
FlashCanvas.initElement(canvases[i]);
}
}
}
I don't understand why it's not working, but canvases[i] throws an [object HTMLUnknownElement] error.
Question:
Any idea what might be the cause? As a workaroud, how could I select the first element of my objectHTMLCollection without using [] and staying in Javascript!
I have also tried adding an id to the canvas element or select it by class (using Jquery). Same result, length=1, select=forget it.
Thanks for help!
EDIT:
I'm requesting plugins like this from my main app controller:
$(document).on('pagebeforeshow', '#basket', function(e, data){
// signaturePad
var signIt = $('.signatureWrapper');
if ( signIt.length > 0 && signIt.jqmData('bound') != true ) {
signIt.jqmData('bound', true);
require(['services/signature/app'], function (App) {
App.render({target: signIt, drawOnly: true });
});
};
This calls an app.js file, which defines all dependencies required and once everything has loaded, fire the plugin:
define([ 'services/signature/app'
, 'services/signature/jquery.signaturepad.min'
, 'services/signature/json2.min'
, 'services/signature/flashcanvas'
], function( app, signature, json2, flashcanvas ) {
function render(parameters) {
parameters.target.signaturePad({ drawOnly:parameters.drawOnly });
};
return {
render:render
};
});
So, I'm wasting an http-request for flashcanvas.js when I don't really need it. But all files are loaded allright, I believe...

How are you adding the canvas element to the DOM? Since IE8 doesn't support the canvas element, you need to create it dynamically and append it to the DOM, as shown in the FlashCanvas docs
var canvas = document.createElement("canvas");
document.getElementById("target").appendChild(canvas);
if (typeof FlashCanvas != "undefined") {
FlashCanvas.initElement(canvas);
}

Array document.getElementsByName(String balise)
http://www.toutjavascript.com/reference/reference.php?iref=156
You wrote :
var canvases = document.getElementsByTagName(CANVAS);
Are you sure CANVAS is a String ? Maybe you want to write
var canvases = document.getElementsByTagName("CANVAS");

Try to convert the collection to an array:
var arr = Array.prototype.slice.call( canvases );

Javascript Variable Sometimes Undefined

I know this question has been asked several times, but I couldn't seem to find a solution that worked for me in any of the previous questions. I have a variable that gets set when my HTML page is done loading, but sometimes when my code tries to access that variable, it says that it is undefined. I'm not sure why, since I believe I am waiting for everything to load properly. This exception seems to happen randomly, as most of the time all the code runs fine. Here's a simplified version of my code:
var globalVar;
function initStuff(filePath) {
// I wait till the HTML page is fully loaded before doing anything
$(document).ready(function(){
var video = document.getElementById("videoElementID");
// My parseFile() function seems to run smoothly
var arrayOfStuff = parseFile(filePath);
if (arrayOfStuff == null) {
console.error("Unable to properly parse the file.");
} else {
setGlobalVariable(arrayOfStuff);
video.addEventListener("play", updateVideoFrame, false);
}
});
}
function setGlobalVariable(arrayOfStuff) {
window.globalVar = arrayOfStuff;
}
function updateVideoFrame() {
// A bunch of other code happens first
// This is the line that fails occasionally, saying
// "window.globalVar[0].aProperty.anArray[0] is undefined"
var test = window.globalVar[0].aProperty.anArray[0].aProperty;
}
The only thing that I can think of that might be causing this problem is some sort of synchronicity issue. I don't see why that would be the case, though. Help please!
Edit:
In case the asynchronicity issue is coming from my parseFile(xmlFile) method, here is what I'm doing there. I thought it couldn't possibly be causing the issue, since I force the method to happen synchronously, but in case I'm wrong, here it is:
function parseKML(xmlFile) {
var arrayOfStuff = new Array();
// Turn the AJAX asynchronicity off for the following GET command
$.ajaxSetup( { async : false } );
// Open the XML file
$.get(xmlFile, {}, function(xml) {
var doc = $("Document", xml);
// Code for parsing the XML file is here
// arrayOfStuff() gets populated here
});
// Once I'm done processing the XML file, I turn asynchronicity back on, since that is AJAX's default state
$.ajaxSetup( { async : true } );
return arrayOfStuff;
}

The first thing you should do in your code is figure out which part of:
window.globalVar[0].aProperty.anArray[0]
is undefined.
Since you have multiple chained property references and array references, it could be many different places in the chain. I'd suggest either set a breakpoint right before your reference it examine what's in it or use several console.log() statement sto output each nested piece of the structure in order to find out where your problem is.
console.log("globalVar = " + globalVar);
console.log("globalVar[0] = " + globalVar[0]);
console.log("globalVar[0].aProperty = " + globalVar[0].aProperty);
console.log("globalVar[0].aProperty.anArray = " + globalVar[0].aProperty.anArray);
console.log("globalVar[0].aProperty.anArray[0] = " + globalVar[0].aProperty.anArray[0]);
If the problem is that globalVar isn't yet set, then you have a timing problem or an initialization problem.
If the problem is that one of the other properties isn't set, then you aren't initializing globalVar with what you think you are.
You may also want to write your code more defensibly so it fails gracefully if some of your data isn't set properly.

You need to use defensive programming.
http://www.javascriptref.com/pdf/ch23_ed2.pdf
Example:
var video = document.getElementById("videoElementID") || 0;
-
if( video && video.addEventListener ){
video.addEventListener("play", updateVideoFrame, false);
}
Here's another version of your code.
window.globalVar = globalVar || [];
function setGlobalVariable(arrayOfStuff) {
window.globalVar = arrayOfStuff;
}
function updateVideoFrame() {
// A bunch of other code happens first
// This is the line that fails occasionally, saying
// "window.globalVar[0].aProperty.anArray[0] is undefined"
if( window.globalVar ){
var g = window.globalVar || [];
var d = (g[0] || {})["aProperty"];
// etc...
}else{
console.error( "test error." );
}
}
function initStuff(filePath) {
// I wait till the HTML page is fully loaded before doing anything
$(document).ready(function () {
var video = $("#videoElementID");
// My parseFile() function seems to run smoothly
var arrayOfStuff = parseFile(filePath) || [];
if (arrayOfStuff == null || video == null ) {
console.error("Unable to properly parse the file.");
} else {
setGlobalVariable(arrayOfStuff);
video.bind("play", updateVideoFrame);
}
});
}

Jquery error in IE

i have been trying to figure this out for the past couple hours and was hoping someone here could help out. I am using JQuery 1.6.4 to make an ajax call when a button is clicked and populate the contents of a table with the results. The code works as it should in all browsers except IE. When i run it in IE, some values are populated and the rest are not, very strange!
When i run the script and use IE's debugging tool i get the following error;
Unexpected call to method or property access (line 3)
Does anyone know what i'm doing wrong? Here is my code that runs the ajax;
$(document).ready(function(){
$("#find").click(function () {
//Set kinase
var kinaseEntry = $("#kinaseEntry").val();
var dataString = "kinaseEntry=" + kinaseEntry;
//Fetch list from database
$.ajax({
type : "GET",
url : "http://www.webaddress/php/post.php",
datatype: "json",
data: dataString,
success : function(datas) {
//SET VARIABLES TO BE USED THROUGHOUT PAGE
var kinaseName = (datas.skuName);
var molecularWeight = (datas.molecularWeight);
var kinaseConc = (datas.kinaseConc);
var anti1Name = (datas.antiName);
var anti2Name = (datas.antiName2);
var antiConc = (datas.antiConc);
var antiConc2 = (datas.antiConc2);
var tracerName = (datas.tracerName);
var tracerConc = (datas.tracerConc);
var tracerStockConc = (datas.tracerStockConc);
var tracerSku = (datas.tracerSku);
var kinaseSku = (datas.kinaseSku);
var antiSku = (datas.antiSku);
var antiSku2 = (datas.antiSku2);
var bufferName = (datas.bufferName);
var bufferSku = (datas.bufferSku);
//REAGENT NAMES
$(".kinaseName").html(kinaseName + " (" + molecularWeight + " kDa)");
$(".anti1Name").html(anti1Name);
$(".anti2Name").html(anti2Name);
$(".tracerName").html(tracerName);
$(".bufferName").html(bufferName);
//DEFAULT VALUES
$(".defaultKinaseConc").html(kinaseConc);
$(".defaultAntiConc").html(antiConc);
$(".defaultAnti2Conc").html(antiConc2);
$(".defaultTracerConc").html(tracerConc);
$("#molecularWeight").val(molecularWeight);
$("#tracerStockConc").val(tracerStockConc);
//INSERT DEFAULTS INTO INPUT
$("#userKinaseConc").val(kinaseConc);
$("#userAntibodyConc1").val(antiConc);
$("#userAntibodyConc2").val(antiConc2);
$("#userTracerConc").val(tracerConc);
},
error : function (XMLHttpRequest, textStatus, errorThrown) {
console.log("error :"+XMLHttpRequest.responseText);
}
});
return false;
}); });
The names populate fine and the first default value gets populated, but the rest breaks. Any help would be greatly appreciated.
Here are the results of my console.log();
antiConc
"2"
antiConc2
"2"
antiName
"Biotin-anti-His"
antiName2
"Eu-Streptavidin"
antiSku
"PV6089"
antiSku2
"PV5899"
bufferName
"Kinase Buffer A"
bufferSku
"PV3189"
cleanSKU
null
kinaseConc
"5"
kinaseSku
"P3049"
molecularWeight
"125.4"
skuName
"ABL1"
tracerConc
"100"
tracerName
"Kinase Tracer 1710"
tracerSku
"PV6088"
tracerStockConc
"25"

Are you sure it's working properly in other browsers, or are they just not breaking as significantly.
I'm guessing you have mixed updates happening here (a distinction presumed from val() and html() use). I notice a pattern whereby elements retrieved by id (e.g., #userKinaseConc) and those retrieved by class (e.g., .kinaseName) are using val() and html() respectively. However, #defAntiCon breaks that pattern. You're using html() for this element. Is this element an input or other form field? Should this be val()?
The experience you describe can be re-created by attempting to apply a value to an input field via html() setter rather than val(), with the exception that it still doesn't work for that specific field in all values... browsers other than IE just fail differently and the error becomes non-breaking. In IE, it will break execution. Is #defAntiCon actually being populated based on data returned in other browsers?

IE8 Is strict about HTML insertion. If your markup is invalid, or either have HTML5 specific tags, it will throw an error.
I have no real solution, but I'd follow this steps to make it works.
Make sure your datas contains valid HTML, make sure you have no extra closing tags or syntax error (you can use a validator if needed)
If you are using HTML5 tags, you could try to use html5shiv to make sure the browser will understand all the tags
Make sur you don't use .val() instead of .html() in some cases
You should replace .html(datas.foo) by .text(datas.foo) since you are passing string to the method.
In case you don't find any solutions, you could add a catch block in jQuery resolveWith method (referring to your comment) by doing the following changes :
replace this :
resolveWith: function ( context, args ) {
if ( !cancelled && !fired && !firing ) {
// make sure args are available (#8421)
args = args || []; firing = 1;
try {
while ( callbacks[ 0 ] ) { callbacks.shift().apply( context, args ); }
} finally {
fired = [ context, args ];
firing = 0;
}
}
return this ;
},
with this :
resolveWith: function ( context, args ) {
if ( !cancelled && !fired && !firing ) {
// make sure args are available (#8421)
args = args || []; firing = 1;
try {
while ( callbacks[ 0 ] ) { callbacks.shift().apply( context, args ); }
} catch (err) {
} finally {
fired = [ context, args ];
firing = 0;
}
}
return this ;
},
Bug on the try-finally in IE is reported here
Hope this helps.
Edit : As #Josh mentionned in the comment, the bug has been reported and resolved in this commit for jQuery 1.7.x. A simple update of your jQuery should works.

External interface and Internet Explorer 9 issue

Boy-oh-boy do I hate external interface. I have a video player that utilizes external interface to control the flash object and to allow the flash object to pass messages to the same javascript. For a time it worked well in all browsers. Then a few days ago i went to go test it in all browsers before i moved the project out of development, and found that the application broke in internet explorer 9. The following error appeared in the console:
SCRIPT16389: Could not complete the operation due to error 8070000c.
jquery.min.js, line 16 character 29366
My javascript file is really long but here are the important parts. All my actions are contained in an object that i created. Inside one of my methods i have the following lines:
var that = this;
that.stop();
here are all the methods that get called as a result of that method:
this.stop = function(){
var that = this;
console.log('stop called');
that.pause();
that.seek(0);
that.isPlaying = false;
console.log('stop finished');
};
this.pause = function(){
var that = this;
console.log('pause called');
if(that.player == 'undefined' || that.player == null){
that.player = that.GetMediaObject(that.playerID);
}
that.player.pauseMedia(); //external interface call
that.isPlaying = false;
console.log('pause finished');
};
this.seek = function(seek){
var that = this;
console.log('seek called');
if(that.player == 'undefined' || that.player ==null){
console.log("player="+that.player+". resetting player object");
that.player = that.GetMediaObject(that.playerID);
console.log("player="+that.player);
}
that.player.scrubMedia(seek); //external interface call
console.log('seek finished');
};
//this method returns a reference to my player. This method is call once when the page loads and then again as necessary by all methods that make external interface calls
this.GetMediaObject = function(playerID){
var mediaObj = swfobject.getObjectById(playerID);
console.log('fetching media object: ' +mediaObj );
//if swfobject.getObjectById fails
if(typeof mediaObj == 'undefined' || mediaObj == null){
console.log('secondary fetch required');
var isIE = navigator.userAgent.match(/MSIE/i);
mediaObj = isIE ? window[playerID] : document[playerID];
}
return mediaObj;
};
Here's the output from my console.log statments:
LOG: fetching media object: [object HTMLObjectElement]
LOG: video-obj-1: ready
LOG: stop called
LOG: pause called
LOG: pause finished
LOG: seek called
LOG: player=[object HTMLObjectElement]
SCRIPT16389: Could not complete the operation due to error 8070000c.
jquery.min.js, line 16 character 29366
The interesting thing is that it appears that the first external interface call 'that.player.pauseMedia()' doesn't have any issue, but the subsequent call to 'that.player.scrubMedia(0)' fails. Another odd thing is that it points to jquery as the source of the error, but there's no call to jquery in those functions.
Here's what i know it's not. It is not an issue where my timing is off. The last line of my actionscript sends a message to the javascript when the flash object has completely loaded. Also i set the parameter 'allowScriptAccess' to 'always' so it's not that either. The actionscript file we use has been used in previous projects so i am 90% certain that that is not the issue.
here's my actionscript anyways. I didn't write actionscript and i'm not too familiar with the language but I tried to put in the parts that seemed most pertinent to my application:
flash.system.Security.allowDomain("*.mydomain.com");
import flash.external.ExternalInterface;
// variables to store local information about the current media
var mediaEmbedServer:String = "www";
var mediaPlayerID:String;
var mediaFile:String;
var mediaDuration:Number;
// variables to be watched by actionscript and message javascript on changes
var mediaPositions:String = "0,0"; // buffer position, scrub position
var mediaStatus:String;
var netStreamClient:Object = new Object();
netStreamClient.onMetaData = metaDataHandler;
netStreamClient.onCuePoint = cuePointHandler;
var connection:NetConnection;
var stream:NetStream;
var media:Video = new Video();
// grab the media's duration when it becomes available
function metaDataHandler(info:Object):void {
mediaDuration = info.duration;
}
function cuePointHandler(info:Object):void {
}
connection = new NetConnection();
connection.addEventListener(NetStatusEvent.NET_STATUS, netStatusHandler);
connection.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler);
try {
var paramName:String;
var paramValue:String;
var paramObject:Object = LoaderInfo(this.root.loaderInfo).parameters;
for (paramName in paramObject) {
paramValue = String(paramObject[paramName]);
switch (paramName){
case "server":
mediaEmbedServer = paramValue;
break
case "playerID":
mediaPlayerID = paramValue;
break
}
}
} catch (error:Error) {
}
if (mediaEmbedServer == "dev" || mediaEmbedServer == "dev2"){
connection.connect("rtmp://media.developmentMediaServer.com/myApp");
} else {
connection.connect("rtmp://media.myMediaServer.com/myApp");
}
function securityErrorHandler(event:SecurityErrorEvent):void {
trace("securityErrorHandler: " + event);
}
function connectStream():void {
stream = new NetStream(connection);
stream.soundTransform = new SoundTransform(1);
stream.addEventListener(NetStatusEvent.NET_STATUS, netStatusHandler);
stream.client = netStreamClient;
media.attachNetStream(stream);
media.width = 720;
media.height = 405;
addChild(media);
}
function netStatusHandler(stats:NetStatusEvent){
switch (stats.info.code){
case "NetConnection.Connect.Success":
connectStream();
break;
case "NetConnection.Call.BadVersion":
case "NetConnection.Call.Failed":
case "NetConnection.Call.Prohibited":
case "NetConnection.Connect.AppShutdown":
case "NetConnection.Connect.Failed":
case "NetConnection.Connect.InvalidApp":
case "NetConnection.Connect.Rejected":
case "NetGroup.Connect.Failed":
case "NetGroup.Connect.Rejected":
case "NetStream.Connect.Failed":
case "NetStream.Connect.Rejected":
case "NetStream.Failed":
case "NetStream.Play.Failed":
case "NetStream.Play.FileStructureInvalid":
case "NetStream.Play.NoSupportedTrackFound":
case "NetStream.Play.StreamNotFound":
case "NetStream.Seek.Failed":
case "NetStream.Seek.InvalidTime":
// report error status and reset javascriptPlay
clearInterval(progressInterval);
messageStatus("error");
break;
default:
// check time through file to determine if media is over
if (stream.time > 0 && stream.time >= (mediaDuration - .25)){
// reset media if it has ended
clearInterval(progressInterval);
stream.play(mediaFile, 0, 0);
messageStatus("finished");
}
}
};
var progressInterval:Number;
// respond to a play/pause request by playing/pausing the current stream
function pauseMedia(){
clearInterval(progressInterval);
if (mediaStatus == 'playing'){
stream.pause();
messageStatus("paused");
}
};
ExternalInterface.addCallback( "pauseMedia", pauseMedia );
// respond to a scrub request by seeking to a position in the media
function scrubMedia(newPosition){
clearInterval(progressInterval);
if (mediaStatus == "playing"){
stream.pause();
messageStatus("paused");
}
stream.seek(newPosition * mediaDuration);
var positionSeconds = newPosition * mediaDuration;
messagePositions(positionSeconds+","+positionSeconds);
};
ExternalInterface.addCallback( "scrubMedia", scrubMedia );
ExternalInterface.call("MediaPlayerReady", mediaPlayerID);

Sounds like an undefined expando property which may be caused by a jQuery IE9 bug. The best way to debug it is to remove the userAgent test and replace it with a check for the object element, such as:
document.getElementsByTagName("object")[0].outerHTML
to see whether the ID attribute is being changed after the first click by jQuery.

I had this problem using JPEGCam, which also uses flash's external interface. My webcam control was being loaded dynamically within a div, and would then throw this error in IE (not firefox or chrome). After moving the initialization of my flash control to document.ready in the parent page, then hiding/showing/moving the control as needed, i was able to work around this exception.
Hope that helps.

Pushlets working with HTML5 canvas or Javascript

Does anyone have experience with Pushlets?
I have been working on it several days. I can make it work on regular javascript, but when I add HTML canvas and use javascript to draw something based on the "push"ed data, it doesn't work.
In my simple example:
document.getElementById('sometag').innerHTML = event.get("x");
document.getElementById('sometag').innerHTML = event.get("x");
...
document.getElementById('sometag').innerHTML = event.get("x");
if I keep all these regular tag there is no problem, but when I add:
document.getElementById('canvas').getContext('2d').fillRect(....);
it doesn't work. The error says can not receive XML data.
So any help? Thanks in advance.

You probably need to evaluate scripts in HTML pushed from server. Something like this:
function extractScripts(html) {
// based on PrototypeJs
var ScriptFragment = "<script[^>]*>([\\S\\s]*?)<\/script>";
var matchAll = new RegExp(ScriptFragment, "img");
var matchOne = new RegExp(ScriptFragment, "im");
return (html.match(matchAll) || []).map(function(scriptTag) {
return (scriptTag.match(matchOne) || ['', ''])[1];
});
}
function evalScripts(html) {
return extractScripts(html).map(function(script) { return eval(script) });
}