For some problems in changing the three methods that this points to in JavaScript, bind, apply, and call

As shown in the figure code
Add... Before passing in a function ~ And declare a variable return Will return a -1, Declare a variable and return It will return a -1- Parameters
Add... Before passing in a function ! And declare a variable return Will return a false, If you put return Comments will return a true
Similarly, if the front becomes + perhaps - Will return to NaN
This is what I found while learning and trying , I hope I can help solve