In Javascript, like setInterval(draw,20) you don't include anything like in C#. You can just use the function. The function is on the Windows object of the browser.
Can the following objects and its functions be called without any pre-definitions?
Window
Navigator
Screen
History
Location
Does JavaScript has any built-in functions?
In Javscript, there are certain things which are part of the language and will also be there. Native objects, like Array(), String() and Number(). (Not a complete list). These need no prefix in front of them, because there are none.
In addition, when running on the browser the host environment provides a global variable called window that is the same as the anonymous Javascript global that everything runs in. Methods of the window object include things like alert() and setTimeout()
Alert can be called with window.alert() or more often by just alert() itself. (Some people consider calling window.alert() best practice to a) show you are calling the global function and b) protect you from any local variables named alert.)
Clarification:
The Javascript engine keeps a global variable with no name and not normally accessible. When not running in struct mode, undeclared variables are created as properties in this global object, all global functions are put in the global object and this normally called functions points to the global object.
When running in the browser, window is the global object.
window. See: jsfiddle.net/3dy8S window is default to a more specific scope (in browser clients). The thing is, there's a base scope, and window in browsers is that scope.global object.window.In short, yes to both :)
Assuming you're interested in client side javascript (running on a webpage within a browser), I strongly suggest you follow the tutorials on code academy, which will answer your questions by teaching you how Javascript works, how you interact with the browser, and what the functions and methods the browser makes available to you.
Once you've finished the tutorial, things should be a lot clearer, and since you already know C# it shouldn't take too long to adjust.
:)
C#tag in case someone with both C# and Javascript skills can help here.