strange anonymous javascript function call

This question already has an answer here:

What does the exclamation mark do before the function? 9 answers

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And you are right, it is an Immediately-Invoked Function Expression (IIFE)

You can rewrite

!+-+-+!+-+-+!+-+-+!+-+-+!+-+-+!+-+-+!+-+-+!+-+-+!
function(d, w){
   ...
}(document, window);

to

!function() {
    ...
}()

and it still works. This is because ! is a unary operator (just like + , - , and ~ -- see https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Expressions_and_Operators). After an unary operator an expression is expected (and evaluated!). The expression can be a function call.

However

!function() {
    ...
}()

is just another expression, so you can put another unary operator in front of it:

+!function() {
    ...
}()

You can continue this pattern as you wish.

Note: Invoking an anonymous function this way, ignores the return value of the function. So only use this, if you are not interested in the return value.

Edit: Added an excellent reference to http://benalman.com/news/2010/11/immediately-invoked-function-expression/ which Daff mentioned in his answer.

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The trick is actually the single ! operator there (the entire first line actually does the same thing). This will work just as well:

!function(d, w){
   ...
}(document, window);

As always I can recommend Ben Almans great article on Immediately-Invoked Function Expressions

链接地址: http://www.djcxy.com/p/17426.html

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