​x
 
<!DOCTYPE html>
<html>
<body>
​
<h1>JavaScript ES5 对象</h1>
​
<p>一个计数器实例</p>
​
<p id="demo"></p>
​
<script>
// 定义对象
const obj = {counter:0};
​
// 定义 setter
Object.defineProperty(obj, "reset", {
  get : function () {this.counter = 0;}
});
Object.defineProperty(obj, "increment", {
  get : function () {this.counter++;}
});
Object.defineProperty(obj, "decrement", {
  get : function () {this.counter--;}
});
Object.defineProperty(obj, "add", {
  set : function (value) {this.counter += value;}
});
Object.defineProperty(obj, "subtract", {
  set : function (i) {this.counter -= i;}
});
​
// 操作计数器：
obj.reset;
obj.add = 5;
obj.subtract = 1;
obj.increment;
obj.decrement;
​
// 打印
document.getElementById("demo").innerHTML = "当前对象计数为：" + obj.counter;
</script>
​
</body>
</html>