Javascript 只读属性

是否可以将javascript对象属性设置为只读？我想设置一个无法修改的属性…

这是可能的，但代价很高。您可以通过拥有一个真正私有的成员变量，然后提供一个访问器函数来实现：

var NiftyThing = function() {
    var trulyPrivateVariable;

    trulyPrivateVariable = 5; // For instance
    this.accessorFunction = function() {
        return trulyPrivateVariable;
    }
};

这是因为访问器函数是var的闭包。代价是每个实例都有自己的访问器函数副本

编辑：用法：

var n = new NiftyThing();
alert(n.trulyPrivateVariable);
// Alerts "undefined"
alert(n.accessorFunction());
// Alerts "5"

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有关更多信息，请参阅。

我同意答案，并希望注意一些JavaScript框架支持此类内置机制：

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，如果您对属性有特殊的需求，例如特定的get访问器实现需求，那么最好定义一个函数，该函数根据需要获取值

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Tengiz

您可以使用Object.defineProperty（）实现类似的功能：

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"
});

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尽管如此，请注意accessorFunction可以被确定的用户覆盖。虽然它不会影响trulyPrivateVariable，但它会影响调用accessorFunction的任何东西。