I am working on a site that has loads of legacy Javascript and jQuery includes and there is no documentation to show what is happening when.
I have a specific problem to fix and I cannot find the relevant code that is being executed when a button is clicked. To save me from trawling through (and making sense of) hundreds of lines of legacy script, is there a feature, possibly in Firebug, that will identify what script is being executed when I click on a button?
I believe there is a feature in Firebug's console window called Profile. Click profile, click the button, then click profile again. It should give you what all functions were called in that time. Be warned that if this code includes jQuery, you might get a huge long list of functions because jQuery uses tons in its code. Unfortunately, the profiler will also show anonymous functions, which can really be a pain.
Otherwise, do a search in the code for the button's class or ID and go through them. If you have an id of fancy then you might do a search for #fancy in your code and attempt to find it. That may lead you in a general direction, at least.
You can click Firebug's "Break on next" button (in the Script tab; it looks like a pause button), then push the button that you want to debug.
The next time any JavaScript code executes, Firebug will break into the debugger and show you that line of code.
The break button didn't work for me. Instead I did edit the onclick attribute with FireBug and prepended it with "debugger;" ... then you'll break right there once you click :)
None of the above answers worked for me. I am trying to use Firebug to figure out how a feature on a page is working for a site I have no control over. Here is what worked for me.
First, got the id of the element I am clicking on from the page source, and then get a temporary reference to it by creating a watch (under the script tab):
tmp=document.getElementById("idOfElement")
Next, I assigned the current onclick value to another temporary variable.
oldfunc=tmp.onclick
Next, I defined a new onclick function. Initially I tried putting debugger; as the first thing in the function, but this does not work! So instead, I created an alert:
tmp.onclick = function() { alert("Ok"); oldfunc() }
Now, as soon as I click on the button the alert comes up, at which point I then click the "Break on next" button as outlined in another answer to this question. Then I dismiss the alert and immediately I am in the debugger at the correct place.
In my case, the "Break on next" button did not work by itself, because there are a lot of other events, just mousing over the page was causing the breakpoint to be hit, preventing me from ever clicking the button.
In Firebug you can set a breakpoint in some JS and then you get a stack which will let you know the current function call stack. So if you set the breakpoint in function used by several handlers then you can use this to discover exactly which handler you are in.
This probably won't work if you are dealing with AJAX callbacks and the like though.
Related
Recently we implemented the GoogleTagManager (GTM), and certain Jquery UI dialogs are not showing at all (some of them always work, some of them never work, consistently). Unfortunately, I cannot provide sample codes.
When a UI button is clicked that calls .dialog("open") the dialog is not shown but the entire page goes grey (div class="ui-widget-overlay ui-front"). I see in the html that the div has "display:none" style.
If I remove the display: none, the dialog is finally shown, but the form's UI is messed up. Somehow the width of the modal is 300px instead of 1000px, etc. Also, the event listeners from the save/cancel buttons are missing. If I put autoOpen: true on the jquery UI dialog declaration, the dialog is shown, but is still messed up the same way.
I noticed that when I have an adblocker, everything works properly, but when I don't, the bug appears. I also realized that a "fbevents.js" file is in the browser when GTM is used, and if I explicitly disable only this file with an adblocker, the bug disappears.
I also see a facebook.com/tr/ call that stays "pending" forever in the network tab in Chrome, when I click on the icon that calls the dialog("open").
And of course, if there is no GTM, the site works properly.
Do you have any idea what is this bug or how should I continue the investigation? (without updating jquery/jqueryUI or without switching to bootstrap modal)?
Without additional detail is very hard to guess, what causes your problem, but there is one thing, I will try ona first place.
Check, how is your trigger made.
There are some GTM configurations, that steps into link click event processing.
So maybe, there is an event listenning on an A element, that onlky pretends to be a link and GTM is waiting for response.
If this is a true, try to change event listener into just Generic click event (Click - All Elements).
I got lucky. I found a second form that exists for a short period of time, which was facebook related (GTM). I realized that a "xy.appendTo('form')" JS code inserts data into the wrong form... By changing the code to "xy.appendTo('#form1')" the problem is gone.
So a simple appendTo('form') started the domino effect, which resulted in duplicated IDs in the DOM, and messed up everything...
The facebook.com/tr call in the network tab is still in pending state, but I believe that is somehow related to Jakub Kriz's suggestion (I will update my answer soon).
UPDATE:
Even though the GTM debugger shows no trigger has been fired, the GTM sends requests to facebook.com/tr calls every time a "a/a href" or "input type="button"" is clicked. I believe this is a default functionality, and I understand why.
In some cases our website is using these html tags in an invalid way: "a" is used instead of a "div" and "input type button" is used for an icon that opens a modal dialog. If we change these, the unnecessary facebook.com/tr calls will be gone.
But I've got still no clue about the pending state. I believe when I apply the changes I mentioned above, the problem will be gone.
I'll pick Chrome for this example, but I'm open to a solution from any browser.
Use Case:
I have an update button on my website that is used to update item quantities in a shopping cart. I'd like to allow a user to enter a 0 and click update in order to remove the item. Trouble is, there is some listener in some js function that is denying the ability to enter a 0 and click update (after clicking update the old quantity remains).
My question is, what developer tool can I use to find which js function is running during that event? I don't think that Chrome's inspector does this, and I'm not very familiar with Firebug, but I couldn't find the functionality there either.
I feel that I should be able to inspect js firings just like I do css stylings. Is anyone aware of a tool I may use?
I've had to debug some particularly nasty unseen-cause Javascript issues at my job. Knowing the full depth of developer tools like Chrome's is definitely helpful. It undeniably takes some creativity to find places that might be causing the issue, but a few tips:
Tracking down event listeners
Under Chrome's Elements view, try Inspect-ing an element (right-click, Inspect); then, on the right side of the developer view, scroll down to Event Listeners. Here you can view what code files have hooked up an event. Often, this will just point you to a middle-framework from the really devious code you're looking for, but sometimes it will point you in the right direction.
Trapping a DOM modification
Many of the unwanted effects I see are because of something changing some value or attribute on the page that I don't want. Anytime this happens, you can right-click on the element (under the Elements view) and say "Break on..." and the specific scenario you're looking for. When Chrome then hits a breakpoint, you can then look downward in the Stack Trace until you find something recognizable that shouldn't be called.
EDIT after reaching ten votes!
Trapping a JS object modification
If the change you're interested in is code-internal, not in the UI, things get trickier. What's meant by this scenario is that you know somewhere in the code, something incredibly annoying like the following is happening.
company.data.myObject.parameter = undefined;
In this situation, you know myObject is still the same object, but it's being modified, perhaps unintentionally. For that, I often insert the following bit of code, sometimes just through the developer console at some point before said modification happens.
Object.defineProperty(company.data.myObject, 'parameter', {
set: (val) => {
debugger;
}
});
This includes an arrow function - you're only using this for debugging and Chrome supports it, so might as well save keystrokes. What this will do is freeze your debugger as soon as some line of code attempts to modify myObject's "parameter" property. You don't necessarily have to have a global reference to the variable if you can run this line of code from a previous breakpoint that will have the given object in the locals.
Otherwise, if all I'm starting out with is the HTML code, and I want to tie that to Javascript code, I'll often just look for identifying features like "id" elements, and search all JS files in my development directory for it. Normally, I can reach it pretty fast.
Open your page in Firefox with Firebug enabled.
Go to console tab in firebug and click profiling
enter 0 in the textbox and click the button.
Stop profiling.
You will be able to see all the javascript functions which have executed due to your actions. You can view them one by one to figure out which method has caused the mischief.
Go to you code. If you are using jQuery there is going to be a function that will be called with the class or id of that particular update button. Or, if you are using Javascript, there is going to be a function called inside the
<input type="button" name="update" onclick="update()">
These are the two ways to look for the function that is being called; there is no software that I know
Download Firebug for Mozilla Firefox, open it, click on Net and refresh your website. Than, you can see which files are loaded on the page.
If you want to check on errors and what goes wrong with an explanation, than click on console and refresh the page once again. You will see the errors and on which line it goes wrong.
Note: in your console, you can say hold or stop, so that the js file stops loading. And you can edit the script by clicking on script in Firebug. Debugging is simple, as it says on their official page https://getfirebug.com/javascript
This issue has come up for me a few times:
I write some code that handles an event, for example a click. I click the element and nothing happens. Some other code is calling e.preventDefault() before my code has the chance to handle it.
Question:
Is there a way to find the code that is preventing default that i have overlooked?
I usually solve this by running javascript profiler in firebug and looking at every function that is called during the click (not inside jquery etc) that may be doing the evil. There has to be a better way.
I would put a test alert in the function that is supposed to execute, starting at the top and then moving it downwards after each statement. If the alert doesn't execute at the top of the function I would check your HTML element and how you are selecting it. If everything appears to be good, I would search your files using possible element selectors.
I have a web page that is having some javascript issues. I have tried looking over everything however I have a username field and when you click it (.focus) it should bring up a pop up. I used firebug in firefox to put break points right then the .focus function is called and it it is not fired even though I do focus on the username field. I have also looked over spelling and everything. Cant seem to find the issue. Hope someone can help. One more thing, this issue is happening in all browsers.
page link: http://aliahealthcareer.com/SignUp
Your page has two inputs with id="username".
Repeating ids is invalid html, but the browser kind of ignores it except that $('#username') finds only the first one so your .focus() handler is bound to that one.
The first is within the "login_response" div that is hidden until you click the "Login" option, so if you click "Login" and then click the "Username/Email" field that appears you'll see that your event handler runs.
You have JS issues on load of that page. JS wont work properly thereafter. You need to fix those first.
I'm examining someone else's code and I'm trying to find out what functions are executing when I take certain actions. Is there a way in firebug to do this? (or any other way).
In this particular case I'm trying to find out what happens when I click the 'next' and 'previous' buttons in the editor found at http://trirand.com/blog/jqgrid/jqgrid.html, "Live Data Manipulation >> Navigator" (then clicking the pencil, then the arrows at the bottom).
I've tried grabbing the item I'm clicking and looking at its properties in the console by doing this:
>>> obj = $('#nData')
>>> console.log(obj)
but there doesn't seem to be a handler for click.
What would be wonderful if if there's a way to see what functions are called when I perform an action.
FireQuery may be of some use to you. It hooks into Firebug and displays additional meta-data on all DOM elements which have been modified by JQuery.
You can use Firebug's "Break on next" (the pause looking button in the toolbar)
Then you can the step buttons to move around. Set it to use that, and then click whichever button you want to check the action for.
Since my description probably sucks, check this out.
Edit: This sounds like what you want:
It's primary goal is breaking the Javascript execution at required place in the code that is unknown to the developer beforehand. The typical example, probably well known to most web developers is: "Where in the hell is the code, which is executed if I click this button?".
In firebug, in the Script tab, put a breakpoint in the line you want to inspect. In the right, there is a "Stack" tab where you can see the current stack trace!