如下 求解释 js prototype

Question

function employee(name,job,born){this.name=name;this.job=job;this.born=born;this.salary=12;}let c=123;var bill=new employee('xx','ss','pp');employee.prototype.salary=function(){    return this.born;}alert((bill.salary+'--000---'+employee.prototype.salary()));var alise=new employee('xx','ss','pp');alert((alise.salary+'--000---'+alise.salary()));

Answer 1

第一个是12--000---undefined，employee.prototype.salary()，this.born没赋值，return undefined;
第二个alise.salary()出错，alise.salary是this.salary，为12，employee中有this.salary=12，把employee.prototype.salary覆盖，找的是this.salary(),报错