+ Operator number in JavaScript

In some frameworks, I saw a similar way: + new Date (); I felt a little strange. I checked the relevant information and some help from some netizens. the usage is explained as follows, hoping to help you,Please correct me if this is not suitable.!

1. For reference type objects (I mean String, Date, Object, Array, Function, Boolean), The + operator operation process is as follows!
1. First, call the valueOf method of this object to obtain the returned value.
2. Convert the value A to A number to obtain the final value.

My tests are as follows:

Function w (s ){
Document. writeln ("<br/> ");
Document. writeln (s );
Document. writeln ("<br/> -----------------------------");
}
String. prototype. valueOf = function () {return 1 ;};
W (+ new String ("sss"); // output 1
String. prototype. valueOf = function () {return "";};
W (+ new String ("sss"); // output NaN

Date. prototype. valueOf = function () {return 1 ;};
W (+ new Date (); // output 1
Date. prototype. valueOf = function () {return "";};
W (+ new Date (); // output NaN

Object. prototype. valueOf = function () {return 1 ;};
W (+ {}); // output 1
Object. prototype. valueOf = function () {return "";};
W (+ {}); // output NaN

Array. prototype. valueOf = function () {return 1 ;};
W (+ []); // output 1
Array. prototype. valueOf = function () {return "";};
W (+ []); // output NaN

Var s = function (){};
Function. prototype. valueOf = function () {return 1 ;};
W (+ s); // output 1
Function. prototype. valueOf = function () {return "";};
W (+ s); // output NaN

Boolean. prototype. valueOf = function () {return 1 ;};
W (+ new Boolean (); // output 1
Boolean. prototype. valueOf = function () {return "";};
W (+ new Boolean (); // output NaN

2. For the basic data type, the value is converted to a number.
W (+ 5); // output 5
W (+ true); // output 1
W (+ false); // output 0
W (+ "ss"); // output NaN
W (+ "111"); // output 111