javascript - How Do You Know How To Initialize A Script? -

javascript - How Do You Know How To Initialize A Script? -

2 questions:

1) how know how initialize script? code in spot in js file, have create initializing code scratch, etc?

2) why don't have "activate"/initialize jquery script? other scripts i'm using required activating, why jquery.js doesn't require internal script going?

just trying wrap head around concept, in advance!

in web page, javascript loaded , executed via html tags of:

<script src="scriptfile"></script>

or inline with

<script> ... code here ... </script>

in both/either cases, javascript loaded/found executed top of source way bottom in order found.

there no "initialization" of javascript might found in, say, java or c. there no equivalent of main() function in:

class x { public static main(string args[]) { .... } }

in javascript code starts "executing" top.

it not uncommon see javascript code begin wait dom loaded , prepared. illustration script starts:

$(function() { // ... code here ... });

should read execute function called "$" , pass annonymous function should run when dom has loaded. these symbols, curly braces, brackets , such can confusing best way comprehend them still realize code runs top bottom ... may not run immediately. example:

var x = function() { // ... code ... }; x();

even though there may tons of code within function definition, not run until phone call function made. in javascript separate code definitions code execution.

see related q&a:

main() function in javascript?

javascript jquery initialization