I know there are tools which allow us to debug our own website? How can I debug(or analyze) any website, for eg:- Amazon, Google?
Basically, I want to add print functions(in JS) and add breakpoints (in JS) in the execution of a website. How is that achievable, if at all.
We can live-debug (and play-around) CSS and HTML on the browser itself, but how to debug JS on the browser?
On Google Chrome for exemple, open the DevTools window by pressing F12 and right-click on the HTML element. Then go on Break on -> and choose subtree modifications. Your app will stop at page loading and you will be able to do step by step analysis.
Related
I was doing some modifications in javascript on some website in Google Chrome to see what changes appear on the web page.
What I observed that I am not able to see the complete javascript code on the element tab in developer tools. The same code exists on the Source tab able to modify that but those modification doesn't work at it doesn't work once DOM is loaded. This is the screenshot of what I am getting:
It is in HTML edit mode and this script is part of html page.... at
the end, it is not a complete script.
ScreenShot:
Is there any way to get it complete in element tab or any other way to modify script?
If you right click on the tag and select "Edit as HTML", you'll be able to access the whole script, without the hyphenation.
You won't be able to change Javascript code through the source tab and expect it to run your new code on reload. If you want to run Javascript on a website with Google Chrome Developer Tools, I'd suggest using the console tab and adding the code you'd want to run on the website. It won't save, but it's essentially the same as injecting Javascript to run on a website.
I'm working on a new client's website that loads Javascript from a CDN so the Javascript is not embedded or inline with the webpage source. I would like to pause everytime getCurrentPosition() is executed in order to determine which external JS file it is contained in.
I realize I could use other tools to do a string search through the contents of the JS files but I would rather keep to Chrome's debugging tools.
Should I be trying to create a watch expression or is there another way to pin down when and where a certain JS function is fired?
You can search in all files using Chrome DevTools. Find your function and debug it:
Open DevTools (F12)
Go to sources tab
Open Search All Files by pressing ctrl + shift + f (Win) or cmd + option + f (Mac)
Search getCurrentPosition
Put a breakpoint (By clicking the line number at the left of the line)
Open Google Dev tools(F12)
Press Ctrl + p
In the opened box search for all files(JS, CSS, ...).
In the box you have 5 options:
At the first select a file for using options 2-5
Type 'filename' and select it.
Type ':linenumber' to go to specific line number(':10' go to line 10).
Type '#symbol' to go to specific symbol('#TestSymbol' go to TestSymbol symbol).
In this option, if you write #JSFunctionName or #CSSClassName then the cursor
will navigate to the JSFunctionName or the CSSClassName.
Type '!snippet' to go to specific snippet('!snippetTest' go to snippetTest snippet).
Type '>googleCommand' to go to specific command('>Clear console' clear the console).
You can find all the information that you need at the webpage: https://developer.chrome.com/devtools/docs/javascript-debugging
By simply putting it (copied from the webpage)
Open a site such as the Google Closure hovercard demo page or the TodoMVC
Open a site such as the Google Closure hovercard demo page or the TodoMVC Angular app
Open the DevTools window.
If it is not already selected, select Sources.
Debugging with breakpoints
A breakpoint is an intentional stopping or pausing place in a script. Use breakpoints in DevTools to debug JavaScript code, DOM updates, and network calls.
Add and remove breakpoints
In the Sources panel, open a JavaScript file for debugging. In the example below, we are debugging the todoCtrl.js file from the AngularJS version of TodoMVC.
Click the line gutter to set a breakpoint for that line of code. A blue tag will indicate if a breakpoint has been set:
With the above simple example you can actually "stop" the function getCurrentPosition() and debug it.
One way would be to replace the Geolocation.getCurrentPosition method with a wrapper function so that you can set a breakpoint inside it, and then examine the stack to see who is calling it.
If you know where in the code the method is called you can set breakpoints. This will pause the javascript execution during runtime and allow you get a stack trace.
I'm working on a new client's website that loads Javascript from a CDN so the Javascript is not embedded or inline with the webpage source. I would like to pause everytime getCurrentPosition() is executed in order to determine which external JS file it is contained in.
I realize I could use other tools to do a string search through the contents of the JS files but I would rather keep to Chrome's debugging tools.
Should I be trying to create a watch expression or is there another way to pin down when and where a certain JS function is fired?
You can search in all files using Chrome DevTools. Find your function and debug it:
Open DevTools (F12)
Go to sources tab
Open Search All Files by pressing ctrl + shift + f (Win) or cmd + option + f (Mac)
Search getCurrentPosition
Put a breakpoint (By clicking the line number at the left of the line)
Open Google Dev tools(F12)
Press Ctrl + p
In the opened box search for all files(JS, CSS, ...).
In the box you have 5 options:
At the first select a file for using options 2-5
Type 'filename' and select it.
Type ':linenumber' to go to specific line number(':10' go to line 10).
Type '#symbol' to go to specific symbol('#TestSymbol' go to TestSymbol symbol).
In this option, if you write #JSFunctionName or #CSSClassName then the cursor
will navigate to the JSFunctionName or the CSSClassName.
Type '!snippet' to go to specific snippet('!snippetTest' go to snippetTest snippet).
Type '>googleCommand' to go to specific command('>Clear console' clear the console).
You can find all the information that you need at the webpage: https://developer.chrome.com/devtools/docs/javascript-debugging
By simply putting it (copied from the webpage)
Open a site such as the Google Closure hovercard demo page or the TodoMVC
Open a site such as the Google Closure hovercard demo page or the TodoMVC Angular app
Open the DevTools window.
If it is not already selected, select Sources.
Debugging with breakpoints
A breakpoint is an intentional stopping or pausing place in a script. Use breakpoints in DevTools to debug JavaScript code, DOM updates, and network calls.
Add and remove breakpoints
In the Sources panel, open a JavaScript file for debugging. In the example below, we are debugging the todoCtrl.js file from the AngularJS version of TodoMVC.
Click the line gutter to set a breakpoint for that line of code. A blue tag will indicate if a breakpoint has been set:
With the above simple example you can actually "stop" the function getCurrentPosition() and debug it.
One way would be to replace the Geolocation.getCurrentPosition method with a wrapper function so that you can set a breakpoint inside it, and then examine the stack to see who is calling it.
If you know where in the code the method is called you can set breakpoints. This will pause the javascript execution during runtime and allow you get a stack trace.
I am using javascript for an ascx control in my application.
I am getting some errors and want to debug the same.
I have put the debugger in my javascript and unchecked disable script debugging for internet explorer.
When my script is getting executed, I get the debugger launched, and when I attach the javascript (here it is in a separate file ), There is a message as,
There is no source code available for the current location.
What could be going wrong here.
I hope to get some tips on debugging javascript with ascx control
To debug Javacript embedded in a ascx control, you can use chrome explorer.
Here is the step.
Open the page that has the user control in it.
Press F12 on that page.
go to Sources in the "DevTools"
Find pages in the "Sources" tab
click on the page name that you are debugging.
you will see the source code in the middle pane.
your user control javascript is included in the page's source code, this is the key.
use Ctrl + F to find that javascript by the method name you want to debug
add breakpoints to that method and debug
Hope it helps.
To debug JavaScript, Hit f12 in your browser. This will open the developer tools in most browsers. (with Firefox, this assumes you've already installed firebug, which has to be installed separately as an add-on.)
Select the script tab, set your break points by clicking the margin to the left of the line of code where you want to break. If you are using IE, click "start debugging". Then perform an action on your page that will trigger your code. Happy debugging.
I am using a gwt based ui design framework (called GXT). In the docs for this framework, it is mentioned that running "javascript:isc.showConsole()" when the app is running, will open the developer console in browser.
However when I run this in Chrome it instead does a google search for the command- in firefox it simply does not work.
How do I execute this javascript in firefox or chrome--
javascript:isc.showConsole()
Bookmarklets cannot be executed in the location bar/omnibox any more.
You have to bookmark the javascript: link before it can be executed.
A better solution is using the built-in Developer tools, in which code can be pasted and executed in the current page:
Firefox: Ctrl Shift K - See Using the web console.
Chrome: Ctrl Shift J - See Developer tools.
In Chrome, you add a tab, open bookmarks - click Other Bookmarks, right click in the bookmarks area, click add new page - and paste the URL.
In Firefox, just manage your bookmarks, click on the folder, right click in the bookmarks section and click New Bookmark.
You have to put the command in the URL of the very SmartGWT
application that you're developing, not any blank page.
Making it become a bookmark bar is a good idea, click that bookmark
when you're opening the application will open the console for you.