The plus sign in front of the js function, exclamation point, and plus sign in front of the js Function

The plus sign in front of the js function, exclamation point, and plus sign in front of the js Function

+ Function (){}();

The plus sign can also be replaced !,~ And other unary operators, the effect is equivalent:

(Function () {console. log ("Foo! ") ;}) (); // Or (function () {console. log (" Foo! ");}());

Without this plus sign, the parser considers the function as the beginning of a function declaration, and the following () will cause a syntax error. When the + sign is added before the function, it becomes a function expression, and a () is added after the function expression to become a function that is executed immediately.

Reference: http://stackoverflow.com/questions/13341698/javascript-plus-sign-in-front-of-function-name