debugging - How can I debug javascript on Android?

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Top 5 Answer for debugging - How can I debug javascript on Android?

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91

Update: Remote Debugging

Previously, console logging was the best option for debugging JavaScript on Android. These days with Chrome for Android remote debugging, we are able to make use of all the goodness of the Chrome for Desktop Developer Tools on Android. Check out https://developers.google.com/chrome-developer-tools/docs/remote-debugging for more information.


Update: JavaScript Console

You can also navigate to about:debug in the URL bar to activate the debug menu and the JavaScript error console with recent Android devices. You should see SHOW JAVASCRIPT CONSOLE at the top of the Browser.

Currently in Android 4.0.3 (Ice Cream Sandwich), the logcat outputs to the browser channel. So you can filter using adb logcat browser:* *:S.


Original Answer

You can use the built in console JavaScript object to print log messages that you can review with adb logcat.

console.error('1'); console.info('2'); console.log('3'); console.warn('4') 

Produces this output:

D/WebCore (  165): Console: 1 line: 0 source: http://... D/WebCore (  165): Console: 2 line: 0 source: http://... D/WebCore (  165): Console: 3 line: 0 source: http://... D/WebCore (  165): Console: 4 line: 0 source: http://... 

Determining the version of WebKit

If you type javascript:alert(navigator.userAgent) in the location bar you’ll see the WebKit version listed e.g.

In Chrome: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.2 (KHTML, like Gecko) Chrome/4.0.221.6 Safari/532.2

On Android Emulator Mozilla/5.0 (Linux; U; Android 1.6; en-us; sdk Build/DRC76) AppleWebKit/528.5+ (KHTML, like Gecko) Version/3.1.2 Mobile Safari/525.20.1

N.B.

Versions of WebKit that are not part of a Safari release have a + after the version number, and their version number is generally higher than the latest released version of WebKit. So, for example, 528+ is an unofficial build of WebKit that is newer than the 525.x version that shipped as part of Safari 3.1.2.

vote vote

83

Try:

  1. open the page that you want to debug
  2. while on that page, in the address bar of a stock Android browser, type:

    about:debug  

    (Note nothing happens, but some new options have been enabled.)

Works on the devices I have tried. Read more on Android browser's about:debug, what do those settings do?

Edit: What also helps to retrieve more information like line number is to add this code to your script:

window.onerror = function (message, url, lineNo){     console.log('Error: ' + message + '\n' + 'Line Number: ' + lineNo);     return true; } 
vote vote

71

The http://jsconsole.com ( http://jsconsole.com/remote-debugging.html ) provides a nice way you can use to access the content of you webpage.

vote vote

69

I use Weinre, part of Apache Cordova.

With Weinre, I get Google Chrome's debug console in my desktop browser, and can connect Android to that debug console, and debug HTML and CSS. I can execute Javascript commands in the console, and they affect the Web page in the Android browser. Log messages from Android appear in the desktop debug console.

However I think it's not possible to view or step through the actual Javascript code. So I combine Weinre with log messages.

(I don't know much about JConsole but it seems to me that HTML and CSS inspection isn't possible with JConsole, only Javascript commands and logging (?).)

vote vote

50

Take a look at jsHybugger. It will allow you to remotely debug your js code for:

  • Android hybrid apps (webview, phonegap, worklight)
  • Web pages which runs in the default android browser (not Chrome, it supports the ADB extension without this tool)

How this works (more details and alternatives on the projects site, this was what I found to be the best way).

  1. Install the jsHybugger APK on your device
  2. Enable USB debugging on you device.
  3. Plug the Android device into your desktop computer via USB
  4. Run the app on the Android device ('jsHybugger')
  5. Enter the target URL and page in the app. Press Start Service and finally Open Browser
    • You'll be presented with a list of installed browsers, choose one.
    • The browser launches.
  6. Back on your desktop computer open Chrome to chrome://inspect/
  7. An inspectors window will appear with the chrome debugging tools linked to the page on the Android device.
  8. debug away!

Again, with Chrome on Android use the ADB extension without jsHybugger. I think this already described in the accepted answer to this question.

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