We Keep Coding

Javascript run faster if console opened

i'm developing a phonegap app using a lot of javascript. Now i'm debugging it using Safari Developer Tool, in particular i'm focused on some button that on the device seems to be a bit luggy.
So I've added some console.timeEnd() to better understand where the code slow down, but the "problem" is that when i open the console the code start running faster without lag, if i close it again, the lag is back.
Maybe my question is silly but i can't figure it out
Thanks
EDIT: Added the code
function scriviNumeroTastiera(tasto){
console.time('Funzione ScriviNumeroTastiera');
contenutoInput = document.getElementById('artInserito').value;
if ($('#cursoreImg').css('display') == 'none'){
//$('#cursoreImg').show();
}
else if (tasto == 'cancella'){
//alert(contenutoInput.length);
if (contenutoInput.length == 0) {
}
else {
indicePerTaglioStringa = (contenutoInput.length)-1;
contenutoInput = contenutoInput.substr(0, indicePerTaglioStringa);
$('#artInserito').val(contenutoInput);
//alert('tastoCanc');
margineAttualeImg = $('#cursoreImg').css('margin-left');
indicePerTaglioStringa = margineAttualeImg.indexOf('p');
margineAttualeImg = margineAttualeImg.substr(0, indicePerTaglioStringa);
margineAggiornato = parseInt(margineAttualeImg)-20;
$('#cursoreImg').css('margin-left', margineAggiornato+'px');
}
}
else {
//contenutoInput = document.getElementById('artInserito').value;
contenutoAggiornato = contenutoInput+tasto;
margineAttualeImg = $('#cursoreImg').css('margin-left');
indicePerTaglioStringa = margineAttualeImg.indexOf('p');
margineAttualeImg = margineAttualeImg.substr(0, indicePerTaglioStringa);
margineAggiornato = parseInt(margineAttualeImg)+20;
$('#cursoreImg').css('margin-left', margineAggiornato+'px');
$('#artInserito').val(contenutoAggiornato);
}
console.timeEnd('Funzione ScriviNumeroTastiera');
}
The code is a bit crappy, but it's just a beginning ;)

This could happen because PhoneGap/Cordova creates its own console object (in cordova.js), and it gets overwritten when you open the Safari console (safari's might be faster than phonegap's, that could be why you notice it faster).
So, one way to measure the time properly, without opening the console, would be to go to the good old alert, so you'd first add this code anywhere in your app:
var TIMER = {
start: function(name, reset){
if(!name) { return; }
var time = new Date().getTime();
if(!TIMER.stimeCounters) { TIMER.stimeCounters = {} };
var key = "KEY" + name.toString();
if(!reset && TIMER.stimeCounters[key]) { return; }
TIMER.stimeCounters[key] = time;
},
end: function(name){
var time = new Date().getTime();
if(!TIMER.stimeCounters) { return; }
var key = "KEY" + name.toString();
var timeCounter = TIMER.stimeCounters[key];
if(timeCounter) {
var diff = time - timeCounter;
var label = name + ": " + diff + "ms";
console.info(label);
delete TIMER.stimeCounters[key];
}
return diff;
}
};
(This just mimics the console.time and console.timeEnd methods, but it returns the value so we can alert it).
Then, instead of calling:
console.time('Funzione ScriviNumeroTastiera');
you'd call:
TIMER.start('Funzione ScriviNumeroTastiera');
and instead of calling:
console.timeEnd('Funzione ScriviNumeroTastiera');
you'd call:
var timeScriviNumeroTastiera = TIMER.end('Funzione ScriviNumeroTastiera');
alert('Ellapsed time: ' + timeScriviNumeroTastiera);
This would give you the proper ellapsed time without opening the console, so it computes the real time in the phonegap app.
Hope this helps.
Cheers

This really isn't something you would normally expect - opening the console should not speed up anything. If anything, it will make things slower because of additional debugging hooks and status display. However, I've had a case like that myself. The reason turned out to be very simple: opening the console makes the displayed portion of the website smaller and the code efficiency was largely dependent on the viewport size. So if I am right, making the browser window smaller should have the same effect as opening the console.

.gBrowser is undefined

I'm writing a restartless Firefoxextension where I have to enumerate all open tabs and work with them.
Here's the code-part that throws the error:
getInfoString : function ()
{
infos = "";
HELPER.alerting("url", "URL-Function");
var winMediator = Components.classes["#mozilla.org/appshell/window-mediator;1"].getService(Components.interfaces.nsIWindowMediator);
HELPER.alerting("url", "Mediator initialized");
var mrw = winMediator.getEnumerator(null);
while(mrw.hasMoreElements())
{
var win = mrw.getNext();
var t = win.gBrowser.browsers.length;
HELPER.alerting("url", "browsers: " + t);
for (var i = 0; i < t; i++)
{
var b = win.gBrowser.getBrowserAtIndex(i);
if(b.currentURI.spec.substr(0,3) != "http")
{
continue;
}
HELPER.alerting(b.title,b.currentURI.spec);
var doc = b.contentDocument;
var src = doc.documentElement.innerHTML;
infos = infos + src
HELPER.alerting("doc", src);
}
}
return infos;
}
I have a JavascriptDebugger-Addon running while testing this and Firefox executes everything fine to the line
HELPER.alerting("url", "browsers: " + t);
But AFTER this line, the debugger-addons throws an error, saying that:
win.gBrowser is undefined
... pointing to the line:
var t = win.gBrowser.browsers.length;
But before it throws the error I get my alertmessage which gives me the correct number of tabs. So the error is thrown after the line was executed and not directly WHEN it was executed.
Does anyone has an idea how to fix this, because the extension stops working after the error has been thrown.
Greetz
P.S.: If someone has a better headline for this, feel free to edit it.

Using winMediator.getEnumerator(null) would give you all types of window, that may or may not be browser windows. You should try changing the following line
var mrw = winMediator.getEnumerator(null);
with
var mrw = winMediator.getEnumerator('navigator:browser');

I finally figured out that this behavior can happen sometimes.
I just rearranged the code a bit, removing some alerts inside the for-loop and it works just fine again.
So if someone has this error too, just rearrange your code and it should work like a charm again.

Showing console errors and alerts in a div inside the page

I'm building a debugging tool for my web app and I need to show console errors in a div. I know I can use my own made console like object and use it, but for future use I need to send all console errors to window. Actually I want to catch console events.

To keep the console working:
if (typeof console != "undefined")
if (typeof console.log != 'undefined')
console.olog = console.log;
else
console.olog = function() {};
console.log = function(message) {
console.olog(message);
$('#debugDiv').append('<p>' + message + '</p>');
};
console.error = console.debug = console.info = console.log

Here's a way using closure, containing the old console log function in the scope of the new one.
console.log = (function (old_function, div_log) {
return function (text) {
old_function(text);
div_log.value += text;
};
} (console.log.bind(console), document.getElementById("error-log")));

None of the answers here consider console messages that get passed multiple parameters. E.g. console.log("Error:", "error details")).
The function that replaces the default log function better regards all function arguments (e.g. by using the arguments object). Here is an example:
console.log = function() {
log.textContent += Array.prototype.slice.call(arguments).join(' ');
}
(The Array.prototype.slice.call(...) simply converts the arguments object to an array, so it can be concatenated easily with join().)
When the original log should be kept working as well:
console.log = (function (old_log, log) {
return function () {
log.textContent += Array.prototype.slice.call(arguments).join(' ');
old_log.apply(console, arguments);
};
} (console.log.bind(console), document.querySelector('#log')));
A complete solution:
var log = document.querySelector('#log');
['log','debug','info','warn','error'].forEach(function (verb) {
console[verb] = (function (method, verb, log) {
return function () {
method.apply(console, arguments);
var msg = document.createElement('div');
msg.classList.add(verb);
msg.textContent = verb + ': ' + Array.prototype.slice.call(arguments).join(' ');
log.appendChild(msg);
};
})(console[verb], verb, log);
});
(An example of a framework that emits messages with multiple parameters is Video.js. But there is certainly many others.)
Edit: Another use of multiple parameters is the formatting capabilities of the console (e.g. console.log("Status code: %d", code).
About errors that are not shown
(Update Dec. 2021)
If any code crashes with an uncaught error, in might not show up in the div. One solution could be, if possible, to wrap all code in a try block to catch such errors and log them manually to the div.
try {
// Code that might throw errors...
} catch(err) {
// Pass the error to the overridden error log handler
console.error(err);
}

Else, if you were concerned at keeping log, warn and error separate from one another, you could do something like this (adapted from MST's answer):
var log = document.querySelector('#log');
['log','warn','error'].forEach(function (verb) {
console[verb] = (function (method, verb, log) {
return function (text) {
method(text);
// handle distinguishing between methods any way you'd like
var msg = document.createElement('code');
msg.classList.add(verb);
msg.textContent = verb + ': ' + text;
log.appendChild(msg);
};
})(console[verb].bind(console), verb, log);
});
where #log is your HTML element. The variable verb is one of 'log', 'warn', or 'error'. You can then use CSS to style the text in a distinguishable way. Note that a lot of this code isn't compatible with old versions of IE.

How about something as simple as:
console.log = function(message) {$('#debugDiv').append('<p>' + message + '</p>');};
console.error = console.debug = console.info = console.log

<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<div id="logger" class="web_console"></div>
<script type="text/javascript">
// Overriding console object
var console = {};
// Getting div to insert logs
var logger = document.getElementById("logger");
// Adding log method from our console object
console.log = function(text)
{
var element = document.createElement("div");
var txt = document.createTextNode(text);
element.appendChild(txt);
logger.appendChild(element);
}
// testing
console.log("Hello World...");
console.log("WOW");
/**
console.log prints the message in the page instead browser console, useful to programming and debugging JS using a Android phone
*/
</script>
</body>
</html>

I created a zero-dependency npm module for this case: console-events (surely if you're okay to use nodejs :P)
You can add event listener like that:
const { console } = require('console-events');
console.addEventListener('log', (e) => {
e.preventDefault(); //if you need to prevent normal behaviour e.g. output to devtools console
$('#debugDiv').append('<p>' + message + '</p>');
})

Get the url of currently executing js file when dynamically loaded

So I'm trying to load a script dynamically and figure out the URL path at which that script was loaded. So some guy gave me a pretty awesome solution to this problem if the scripts are statically loaded ( How to get the file-path of the currently executing javascript code ). But I need a dynamically loaded solution. For example:
$(function()
{ $.getScript("brilliant.js", function(data, textStatus)
{ // do nothing
});
});
where "brilliant.js" has:
var scripts = document.getElementsByTagName("script");
var src = scripts[scripts.length-1].src;
alert("THIS IS: "+src);
Ideally this should either print out "brilliant.js" or "〈hostname+basepath〉/brilliant.js"
Currently brilliant.js works for statically included scripts, but not for scripts included dynamically (like with $.getScript). Anyone have any ideas? Is there somewhere in the dom that stores all the scripts that have been loaded?
EDIT: Andras gave a pretty good solution, though it probably only works for jQuery. Since that's probably the most popular library, and definitely what I'm going to be using. It can probably be extended for other libraries as well. Here's my simplified version:
var scriptUri;
curScriptUrl(function(x)
{ scriptUri = x;
alert(scriptUri);
});
function curScriptUrl(callback)
{ var scripts = document.getElementsByTagName("script");
var scriptURI = scripts[scripts.length-1].src;
if(scriptURI != "") // static include
{ callback(scriptURI);
}else if($ != undefined) // jQuery ajax
{ $(document).ajaxSuccess(function(e, xhr, s)
{ callback(s.url);
});
}
}

When your script gets loaded with jQuery (and I guess other frameworks as well), your script will become indistinguishable from a script that was originally in the HTML document. jQuery makes a request reaching out for your script and puts back the reply as the text child of a <script> node. Your browser has no way of knowing where it originated from, whether it was modified before inserted, etc. It is just a script node as far as she is concerned.
There can be workarounds, however. In the case of jQuery, you can hook up to the ajax events and exploit the fact that they are called right after your script executes. Basically, this would yield "brilliant.js" in your example:
var handler = function (e, xhr, s) {
alert(s.url);
}
$(document).ajaxSuccess(handler);
A more elaborate one:
(function ($, undefined) {
/* Let's try to figure out if we are inlined.*/
var scripts = document.getElementsByTagName("script");
if (scripts[scripts.length - 1].src.length === 0) {
// Yes, we are inlined.
// See if we have jQuery loading us with AJAX here.
if ($ !== undefined) {
var initialized = false;
var ajaxHandler = function (e, xhr, s) {
if (!initialized) {
initialized = true;
alert("Inlined:" + s.url);
initmywholejsframework();
}
}
//If it is, our handler will be called right after this file gets loaded.
$(document).ajaxSuccess(ajaxHandler);
//Make sure to remove our handler if we ever yield back.
window.setTimeout(function () {
jQuery(document).unbind("ajaxSuccess", ajaxHandler);
if (!initialized) {
handleInlinedNonjQuery();
}
}, 0);
}
} else {
//We are included.
alert("Included:" + scripts[scripts.length - 1].src);
initmywholejsframework();
}
//Handle other JS frameworks etc. here, if you will.
function handleInlinedNonjQuery() {
alert("nonJQuery");
initmywholejsframework();
}
//Initialize your lib here
function initmywholejsframework() {
alert("loaded");
}
})(jQuery);

B T, sorry if this doesn't help, but I'm curious why you would need to do this? The reason I'm asking is I don't see why you can't just use the relative file paths to load these files? Finding out where you're located could be done with window.location, but why would you? And as for loading them, can't you make an ajax call to the file and then eval them?

This will work in every browser except IE and doesn't depend on assuming what the name of a file is:
var getErrorLocation = function (error) {
var loc, replacer = function (stack, matchedLoc) {
loc = matchedLoc;
};
if ("fileName" in error) {
loc = error.fileName;
} else if ("stacktrace" in error) { // Opera
error.stacktrace.replace(/Line \d+ of .+ script (.*)/gm, replacer);
} else if ("stack" in error) { // WebKit
error.stack.replace(/at (.*)/gm, replacer);
loc = loc.replace(/:\d+:\d+$/, ""); // remove line number
}
return loc;
};
try {
0();
} catch (e) {
var scriptURI = getErrorLocation(e);
}
alert("THIS IS: " + scriptURI);

Drawing a user interface based on preferences

I want to use the built-in preference system for my xulrunner (Firefox) application. But I can't figure out how to easily drive the user interface based on preferences.
The user can specify a list of home pages, and each home page will show up in a different tab. Because the tabs are in the presentation layer, I'd like to create them using a template in the xul code. Is this possible?
I haven't seen a way to do this with xul templates. Is there an alternative templating system that would allow me to change the UI based on user preferences?

No, templating in XUL is not powerful enough, so you're stuck with writing JavaScript code that reads the preferences and opens the needed tabs.

XML.prototype.function::domNode = function domNode() {
function addPrefix(prefix, name) {
if (typeof(prefix) == "undefined" || prefix == null || prefix == "") {
return name;
} else {
return prefix + ":" + name;
}
}
function recurse(xml) {
var domNode = document.createElementNS(xml.namespace().uri, addPrefix(xml.namespace().prefix, xml.localName()));
for each (let attr in xml.#*::*) {
let attrNode = document.createAttributeNS(attr.namespace().uri, addPrefix(attr.namespace().prefix, attr.localName()));
attrNode.nodeValue = attr;
domNode.setAttributeNode(attrNode);
}
if (xml.hasComplexContent()) {
for each (let node in xml.*) {
domNode.appendChild(recurse(node));
}
} else if (xml.hasSimpleContent()) {
domNode.appendChild(document.createTextNode(xml));
}
return domNode;
}
return recurse(this);
};
var name = "example"
var xml = {name};
document.querySelector("#example-statusbar-panel").appendChild(xml.domNode());
works as a charm, there's some minor glitches with namespaces though.
You could always convert dom back to XML with
var str = serializer.serializeToString( xml.domNode() );