Self-executed anonymous function in avascript and avascript anonymous Function

Self-executed anonymous function in avascript and avascript anonymous Function
Self-executed anonymous functions in Javascript
Format:

(Function () {// code })();

Explanation: this is a pretty elegant code (it may be confusing if you see it for the first time :)). The first pair of parentheses in the function () {}) returns the Untitled function to the script, then a pair of empty parentheses immediately execute the returned untitled function, which contains the parameters of the anonymous function.
Here is an example with parameters:

(Function (arg) {alert (arg + 100) ;}) (20); // in this example, 120 is returned.

Important purpose: You can use it to create a namespace. As long as you write all your code in this special function package, the outside will not be accessible unless you allow

(function(){   function $(id){return document.getElementById(id);   }   function __addClass(id,className,classValue){$(id).style.className=classValue;   }   window['mySpace']={};   window['mySpace']['addClass']=__addClass;})();

In the preceding example, you can use this pseudo namespace to encapsulate and protect all your functions, objects, and variables. Besides, because they are in the same function, they can be referenced from each other. To render the protected code, a pair of parentheses tell the browser to immediately execute the returned anonymous function, and assign _ addClass () to a window method during execution, in this way, only addClass can be executed externally, while _ addClass is protected. I can call it like this: mySpace. addClass ('oneid', 'font-width', 'bold ')

Javascript anonymous function parameters

The first execution is the content in the function, because function () {} () is used to execute this function, as to why the error is reported ..

The returned value is undefined, which is equivalent to setInterval (undefined, 1000). An error is reported ..

In js functions, the this pointer of anonymous functions points to the question? Javascript

Well, how to analyze it should all point to windows.

Unless it is the following function, it does not point to windows, but the dom object corresponding to the event:

<Div id = "a"> press </div>
<Script>
Document. getElementById ('A'). onclick = function () {alert (this. innerHTML )};
</Script>

However, such a function is no longer a real anonymous function. For example, you can use:

Document. getElementById ('A'). onclick ();

To call this function;