Javascript code snipets

Check whether a checkbox is checked in Javascript — Checkbox object in HTML has a property checked as boolean - it has true or false, so javascript can check its status easily.
Get file extension in Javascript
Input Text readOnly Property in Javascript — Set a text field to read-only in javascript
Loading javascript file conditionally — If you need to load javascript by the case like domain name, you can do that by getElementByTagName() and appendChild(). For instance, you can run application by the screen width.
Open window in the center of the screen
Run a specific function by certain interval — The setInterval() method calls a function or evaluates an expression at specified intervals (in milliseconds). The setInterval() method will continue calling the function until clearInterval() is called, or the window is closed. The ID value returned by setInterval() is used as the parameter for the clearInterval(obj) method.
Run a specific function by timer in Javascript — Javascript provides a straightforward function setTimeout() to implement timer-based application easily.
Stop timer in Javascript — clearTimeout() can stop the running timer based on the variable. Below code shows the simple example to stop running timer.