What does the "+" sign in front of the function mean in Javascript?

Question

Researching a little about form validation on Bootstrap, found the bootstrap-Validator, in which exactly in the file Validator.js, as you can see, it has the notation +funcion. Observe the code below:

+function($) { 
     /* conteúdo */
}(jQuery);

What is the "+" sign in front of the function in Javascript?

Answer 1

+ is a shortcut, a character of two (), which would be the easiest way to read to invoke a function (...a declaração da função..)().

The + will force the next part to the operator to be interpreted as an expression, ie a function statement and will cause the function to run once it is followed by ().

+function(m) {
  console.log('Olá ' + m + '!');
}('mundo')

Those kind of functions are called IIFE, and this kind of shortened syntax can be done with the converter/operator +, or denial ! or bitwise ~. The idea is to save characters.

!function() {console.log('Usando !');}();

~function() {console.log('Usando ~');}();

-function() {console.log('Usando -');}();

(function() {console.log('Usando ()');})();

Personally I think (function...)() , or the variant (function(){}()), is clearer, and therefore the right way. Therefore not using other operators that have as a function something else, but that as a side effect make the browser to interpret the code and save 1 character.