Menggunakan Javascript Console di Browser yang berbeda?

Chrome:
1. Press either CTRL + SHIFT + I or F12 to open the Developer Tools. 
2. Press ESC (or click on "Show console" in the bottom right corner) to slide the console up.
Note: In Chrome's dev tools, there is a "Console" tab. However, a smaller "slide-up" console can be opened while any of the tabs is active.

Safari:

1. Press CTRL + ALT + I to open the Web Inspector.

2. See Chrome's step 2. (Chrome and Safari have pretty much identical dev tools.)
Note: Step 1 only works if the "Show Develop menu in menu bar" check box in the Advanced tab of the Preferences menu is checked!

IE9:

    Press F12 to open the developer tools.

    Click the "Console" tab.

Firefox:

    Press CTRL + SHIFT + K to open the Web console.
or, if Firebug is installed (RECOMMENDED!):

    Press F12 to open Firebug.

    Click on the "Console" tab.

Opera:
Press CTRL + SHIFT + I to open Dragonfly.

    Click on the "Console" tab.

And to put an end to read this post :
Press ALT + F4 Thank you to agan  XD

Source