I am currently trying to debug a js script in chrome, I put a breakpoint in the script and it breaks properly when I use only one tab, but on a second tab it doesn't break even though I see the break point in the code.
Did you use the pretty print option when viewing the source:
I have noticed that the formatted copy can get out of sync. I remove all of the breakpoints, close both the formatted tab and the original tab (in sources), then open the original, click the pretty print option, and add back my break points.
I haven't looked in depth as to why this is happening, it's just what I've experienced and the work around I found (assuming it's something with the cached version of the formatted source).
you have to open a new debugger window for each tab that you want to debug :)
Related
How do I view all JS objects that I created in chrome? I know if I type window into the console, I will see everything, but where is the tab that is filled with all my things?
I think you might be looking for something like Chrome Breakpoints. Basically, in the developer tools, you will go to 'sources', click the file you are wanting to debug, and set a breakpoint on the line in the file that you want to see your active variables. You do this by simply clicking on the line number. When you reload, the browser will pause execution on this line and you will be able to see all the information you are looking for.
I have some JavaScript that, I believe, is stuck in an infinite loop. I know I can just reload the page, but I have data in a form on the current page that I'd like to keep. The tab is completely unresponsive, so I can't just copy and paste everything and then reload. So is there any way to kill the javascript thread, but keep the DOM in Chrome?
You can open the developer console F12 and stop the script
Open chrome developer tools and go to the sources tab. On the right panel press "pause script execution".
looks like someone had the same problem
Cancel infinite loop execution in jsfiddle
Answer:
With the developer mode, go into resources and find your script and copy and paste it into a text document or a new window. If you can't find it in resources, do a search for a variable or line of code you used.
For example, if there is a slideshow moving along, I can see the HTML changing live in Firebug's HTML tab.
The Console tab only shows things that are console.log()-ged to it, or if there is an error. I would like to see confirmation that each line of the Javascript is getting executed - as well as any output/values that are returned/generated as that happens. Like a little cursor on the left going down line by line as it executes - and stopping as soon as error is encountered?
Use breaking points and debugging in console. You can open your script in firebug and choose lines where you can add breakpoints. Then, you can run your script and see in panel on the right a lot of stuff.
I'm looking at a web page where when I push the submit button on a form, it brings up a new page where it runs some javascript and then closes the window.
Is there any way I can step through the javascript on the new page? I tried setting break on next in Firebug on the first page, but the next page still closes the window.
(I'm open to other tools besides Firebug if neccessary, I just need to step through the javascript)
Update:
I should have mentioned I don't have access to the code :-(
If you have access to the code, you can place this little statement where you want to have a breakpoint:
debugger;
I am not sure about firebug, but I expect it to work there too.
put debugger; in your JavaScript code. and press F12 key just after window open.
I'm currently moving a website from self hosted onto a CMS system. The current site uses a modal popup script called SqueezeBox.js
I've copied the code across exactly how it looks on the current website, however the modal popup box isn't triggering when I click on a thumbnail image.
Looking at the code in the header I've spotted that the CMS I'm using is also calling a number of other javascript files and I'm wondering if one of them is causing a conflict.
What's the best way to find out if this is the case? I've tried Firefox's plugin Web Developer but can't see anything in the Error Console. However I'm not 100% sure I'm using it correctly. Can anyone else point me in the direction of a simple to use javascript conflict detector?
Cheers
Adam
If you have Google Chrome, open up the Developer Tools and you can go into the 'scripts' tab, open up your javascript files and look for the click handler.. click along the side of the code to set a breakpoint, then when the code reaches that spot (if you click it, for example), it will pause, and then in the Developer Tools you can see what functions are being called where as you step through the code. You can also hover over any variable in the code window to see its value. Very handy! You can then see if it's getting into your plugin at all (you can do this as well by setting a breakpoint inside the plugin at a place like the first line that will always be accessed when its run).
I believe you can do the same thing with Firebug
It's a bit of a different thinking process to get into (step into, step over, turning breakpoints on and off etc) but it's extremely useful.
A more simple way of checking where problems are occuring is by adding an alert('im working); or something similar to code you're not sure if it's working. You can also alert a variable to see what the value is at that point. You can also use console command to print it to firebug's console. These are doing things that breakpoints/debugging do for you except with the debugging you don't need to change your code.
If there is a javascript error, then the easies way is using firebug or the Chrome Inspector (right click on the thumbnail and choose "Inspect element"). Open the console tab of either and refresh the page. If there is an error, it will be reported in the console and provide a link to the relevant line.
If there is no error being reported, then the code's logic is preventing the box from being displayed. You'll need to step through the code to find the error. Look at what function is being called from the click handler of the thumbnail image. Go to that function in either tool and place a breakpoint on the first line of the function. Click the thumbnail again and the code will pause on that line. From there you can step through the code and see which code branch is followed. There's likely a sanity check at some point that fails and causes the code to bomb out.