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#11

Put special operators at the beginning of a function

Topics: JavaScript

Usually, we can invoke a function by using the form of Immediately Invoked Function Expression (IIFE).

(function(a, b) {
return a + b;
})(4, 2);

// 6

Do you know that we get the same result if we omit the parentheses and put + at the beginning as follow:

+function(a, b) {
return a + b;
}(4, 2)

// 6

It works because putting + at the beginning of function declaration will turn it to an expression, and passing the parameters with () at the end will invoke the expression.
It is rare to see that code in development, but it is used in the minifications to save the file size.
In addition to +, you can use other operators such as -, !, ~ and void in the similar way to invoke a function:

-function() { ... }();
!function() { ... }();
~function() { ... }();
void function() { ... }();

Note that the return value could be different from the original function, for example:

!function() { return false; }();     // true
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#12 Prefix class name with js to manipulate with javascript