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What does this mean? (function (x,y)){…}){a,b); in JavaScript
(function(){
var foo = 'Hello world';
})();
i don't know what's use of it? and what's meaning of it/?
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3 Answers
On its own it does nothing except declare a variable that isn't used - it should invoke some other functions to do something useful.
That said, what you have is an immediately invoked function expression, i.e. an anonymous function:
function() { ... }
which is invoked with no parameters:
(f....)();
The rationale is two fold:
- it allows the function to be defined and called without giving it a name in the global name space
- any variables defined within the function are also held within that scope, and don't pollute the global name space.
1 Comment
Felix Kling
Every function expression without a name is an anonymous function.
It's an anonymous function that executes immediately.
The idea is to create a private scope. Often one would return a closure from the anonymous function that retains access to variables created in that scope.
For example
var greet = (function () {
var foo = 'Hello world';
return function () {
alert(foo);
}
}());
greet();
Comments
This calls an anonymous function immediately.
Have a look here: What does this “(function(){});”, a function inside brackets, mean in javascript ?
1 Comment
Gabi Purcaru
it's also called a closure sometimes, because all it does is to create a new scope
