() after function call

[Brownie Guy]

Today while researching a bug I found this script:

var Event = {
add: function() {
if (window.attachEvent) {
return function(el, type, fn) {
var f = function() { fn.call(Dom.get(el), window.event); };
Dom.get(el).attachEvent('on' + type, f);
};
}
}()
};

Its the () at the end of the function definition that leaves me
scratching my head. I looked around but I wasn't able to learn the
name of this feature and thus unable to research it farther. Can
someone point me in the right direction or explain it.

Much Appreciated
Travis

[Joost Diepenmaat]

Brownie Guy <tr*************@gmail.comwrites:

Today while researching a bug I found this script:

var Event = {
add: function() {
if (window.attachEvent) {
return function(el, type, fn) {
var f = function() { fn.call(Dom.get(el), window.event); };
Dom.get(el).attachEvent('on' + type, f);
};
}
}()
};

Its the () at the end of the function definition that leaves me
scratching my head. I looked around but I wasn't able to learn the
name of this feature and thus unable to research it farther. Can
someone point me in the right direction or explain it.

Basically, it's just a function call on the anynonymous function.

I.e:

a = {
b: function() { return "result" }()
};

alert(a.b); // note: a.b. is a string, not a function

Note that in some cases you need additional parentheses to make it work:

function(){ alert("call" }(); // error

(function(){ alert("call"} )(); // works

Joost.