js：对象-属性-set/get

碎语：

  js有对象-属性这早已耳熟能详，直到偶然看到某开源js源码才发现，同java一样，它也有对应的set/get方法。

demo：

var che = {
	_wheels: 4,
	get wheels() {
		return this._wheels;
	},
	set wheels(value) {
		if(value < 1) {
			console.log('give me a wheel at least,please!');
		} else {
			this._wheels = value;
		}
	}
};

console.log("che.wheels: "+che.wheels);
console.log("che._wheels: "+che._wheels);

che.wheels = 2;
console.log("che.wheels: "+che.wheels);
console.log("che._wheels: "+che._wheels);

che.wheels = 0;
console.log("che.wheels: "+che.wheels);
console.log("che._wheels: "+che._wheels);

兼容：这种写法并==不支持IE8==，替代方法如下;

var che2 = {
	_wheels: 4
};
Object.defineProperty(che2, "wheels", {
	get: function () {
		return this._wheels;
	},
	set: function (value) {
		if(value < 1) {
			console.log('give me a wheel at least,please!');
		} else {
			this._wheels = value;
		}
	}
});

补充：

传说中的标准写法（不代表常用）

function Field(val){  
    this.value = val;  
} 

Field.prototype = {  
    get value(){  
        return this._value;  
    },  
    set value(val){  
        this._value = val;  
    }
};

var field = new Field("che");
console.log(field.value);

field.value = "che2";
console.log(field.value);

常用写法（外界无法修改默认值）

var che3 = {
	get wheels() {
		return 4;
	}
};

console.log("che3.wheels: " + che3.wheels);

che3.wheels = 2;
console.log("che3.wheels: " + che3.wheels);

最后祝各位程序员，新年吉祥。早！日！脱！单！

参考：网络之美：JavaScript中Get和Set访问器的实现