What does = +_ mean in JavaScript

Question

I was wondering what the = +_ operator means in JavaScript. It looks like it does assignments.

Example:

hexbin.radius = function(_)         


        

Answer 1

It is not an assignment operator.

• _ is just a parameter passed to the function.

  hexbin.radius = function(_) {
                  //       ^ It is passed here
      // ...
  };
  

• On the next line r = +_; + infront casts that variable (_) to a number or integer value and assigns it to variable r

DO NOT CONFUSE IT WITH += operator