[ACCEPTED]-what does !function in Javascript mean?-javascript
It is short-hand or alternative of self-invoking anonymous function:
(function(){
// code
})();
Can 8 be written:
!function(){
// code
}();
You can also use + instead of 7 !.
If you simply did:
function(){
// code
}();
That will create problems, that's 6 why you need to add ! before it which turns 5 the function declaration into function expression.
An ExpressionStatement cannot 4 start with the function keyword because that 3 might make it ambiguous with a FunctionDeclaration.
To 2 better understand the concept, you should 1 check out:
they're negating the result, not the function 6 itself:
!function( x ){ return x }( true );
!true
false
In reality, it's a slightly compressed 5 form of:
(function(){}())
since it requires 1 less character. The 4 reason it's needed is that you can't call 3 a function declaration directly, e.g. this 2 is invalid:
function(){}()
but adding the ! at the beginning 1 turns it into a function expression and makes it work.
It's usually used to work around a quirk 6 in the JavaScript syntax. This gives a syntax 5 error:
function() {
}();
It's read as a function declaration 4 (like function foo () {}), rather than a function expression. So 3 adding the ! before it, or wrapping it in 2 parentheses, forces the parser to understand 1 that it's an expression.
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