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<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>本教程(w3big.com)</title> </head> <body> <script> function employee(name,jobtitle,born){ this.name=name; this.jobtitle=jobtitle; this.born=born; } var fred=new employee("Fred Flintstone","Caveman",1970); employee.prototype.salary=null; fred.salary=20000; document.write(fred.salary); </script> </body> </html>