JavaScript实例教程2

<SCRIPT language="JavaScript">

<!-- Hide from older browsers

function Person(name, age, colour) {

 this.name = name;
 
 this.age = age;
 
 this.colour = colour;
 
 this.birthYear = (new Date()).getYear() - this.age;
 
 this.toString = printPerson; // 这里定义the Person.toString() 方法
 
 this.isOlder = isOlder; // 这里定义Person.isOlder(Person) 方法

}

function printPerson() {

 var text = this.name + " was born in " + this.birthYear +"<br>";
 
 text += "and is " + this.age + " years old.<p>";
 
 return text;

}

function isOlder(otherPerson) { // 这里定义是否第一个人是更老的

return (this.age > otherPerson.age); // 返回布尔型数值

}

//下面的代码用于测试我们的函数

var body1 = new Person("Patrick", 22, "red");

var body2 = new Person("Betty", 21, "green");

document.write(body1); //这里为Person.toString()创建一个调用

document.write(body2);

document.write(body1.name);

document.write((body1.isOlder(body2)) ? " is " : " is not "); // 是否更老？

document.write("older than " + body2.name);

// Stop hiding -->

</SCRIPT>

 

 

 

通过为Person对象重载Person.toString()方法，我们可以将Person对象作为字符串显示出来。每当Person对象被作为字符串引用的时候，pringPerson返回的数值就决定了该显示什么了。