How to debug Javascript code or functions? [closed]

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I have some Javascript code.
I want to trace errors and debug it.
how to do it ?

Debugging is usually done with a debugger... which is present in almost every modern browser. Try pressing F12 or looking over the menus. — user1233508
– user1233508, Commented Sep 12, 2012 at 7:15

Neil · Accepted Answer · 2012-09-12 07:18:03Z

2

It used to be that debugging in javascript was quite limited. You could post alerts to indicate variable states or print information to the web page. In the case of syntax error, it would simply not execute all the code (meaning you had to place alerts prior to the error to know where it was).

Thankfully, browsers have caught up. Firebug is very useful as well as Chrome's developer tools which both use breakpoints, expression evaluation, as well as a series of other useful tools for debugging in-browser. I would suggest you look into these. I believe also internet explorer has a developer tools section, but I've found that it isn't to my liking, however you're free to use whatever you need/require.

answered Sep 12, 2012 at 7:18

Neil

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Joseph · Accepted Answer · 2012-09-12 07:22:16Z

1

It depends on the browser:

Firefox: Download the Firebug Extension
Opera: User the built-in Opera Dragonfly
Webkit-based (Chrome, Safari, Rockmelt...): Press F12 to open the built-in Webkit debugger
Internet Explorer 9+: Press F12 to open the built-in Developer Tools
IE <=8: Install DebugBar

Most of these tools are accessible via these keyboard shortcuts:

CTRL+SHIFT+I
F12

Look for the "Console" Tab. There the browser prints various errors like JavaScript errors, resource not loaded errors etc. To manually write to the console, most browsers offer the console object which hosts functions for the console. Most commonly used is console.log('text').

edited Sep 12, 2012 at 7:22

answered Sep 12, 2012 at 7:16

Joseph

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2 Comments

Hardik Fefar Over a year ago

I have already installed firebug in firefox then how to use it ?

Joseph Over a year ago

@HHF look for the console tab. There the browser prints various errors, including JS errors.

David Horák · Accepted Answer · 2012-09-12 07:23:08Z

0

Google Chrome

F12 -> console.

in code use: console.log(variables);

answered Sep 12, 2012 at 7:23

David Horák

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