只读属性
答
这是可能的，但昂贵。您可以通过具有真正的私有成员变量，然后提供存取功能做到这一点：
var NiftyThing = function() {
var trulyPrivateVariable;
trulyPrivateVariable = 5; // For instance
this.accessorFunction = function() {
return trulyPrivateVariable;
}
};
这工作，因为访问函数是一个封闭在变种。成本是每个实例都有自己的访问函数副本。
编辑：用法：
var n = new NiftyThing();
alert(n.trulyPrivateVariable);
// Alerts "undefined"
alert(n.accessorFunction());
// Alerts "5"
答
我同意了答案，并想指出一些JavaScript框架，如bob.js支持这种内置的机制：
var obj = { };
//declare read-only property.
bob.prop.namedProp(obj, 'name', 'Bob', true);
//declare read-write property.
bob.prop.namedProp(obj, 'age', 1);
//get values of properties.
console.log(bob.string.formatString('{0} is {1} years old.', obj.get_name(), obj.get_age()));
//set value of read-write property.
obj.set_age(2);
console.log(bob.string.formatString('Now {0} is {1} years old.', obj.get_name(), obj.get_age()));
//cannot set read-only property of obj. Next line would throw an error.
// obj.set_name('Rob');
//Output:
//========
// Bob is 1 years old.
// Now Bob is 2 years old.
但是，如果您有任何关于财产的特殊需求，如特定get访问实现需求，然后更好地定义一个函数，根据需要获取价值。
- 吉兹
答
您可以实现这样的事情，利用Object.defineProperty（的）：
function blockProperties(object, properties) {
"use strict";
// If not properties passed, then use the already defined ones:
if (typeof properties === "undefined") {
properties = object;
}
// Loop trough the properties
for (var property in properties) {
if (properties.hasOwnProperty(property)) {
// Make property read-only
Object.defineProperty(object, property, {
value: properties[property],
writable: false,
configurable: false,
enumerable: false
});
}
}
return object;
}
var someObject = {};
blockProperties(someObject, {
propertie1: "someValue",
propertie2: "someOtherValue"
});
someObject.propertie1 = "this doesn't change anything";
console.log(someObject.propertie1); // Output: "someValue"
// Because "window" is also an object, you can set an only-read global var:
blockProperties(window, {
onlyReadVariable: "onlyReadValue"
});
虽然，注意accessorFunction可以通过确定的用户覆盖。虽然它不会影响真正的私人变量，但它会影响任何调用accessorFunction的东西。 – cobbal 2009-08-24 11:01:50