Question

我正在学习OO JavaScript，所以这个问题可能听起来很奇怪。问题：normalize函数应该是私有的，在外面是不可访问/可写的。问题：如何从normalize原型函数中访问prepare？

var AuthHmac = AuthHmac || (function(_, CryptoJS) {
    function AuthHmac(options) {
        var options = options || {},
            normalize = function(s) { return s.toLowerCase(); };

        this.additionalHeaders = options.additionalHeaders || {};
    };

    AuthHmac.prototype.prepare = function(request) {
        request.headers = request.headers || {};

        _.each(this.additionalHeaders, function(value, name) {
            request.headers[this.normalize(name)] = value;
        });
    };

    return AuthHmac;

})(_, CryptoJS);

Answer 1

不，如果normalize函数的作用域是构造函数。

但是，由于您的函数不需要具有特权（即可以访问构造函数的局部变量），因此您可以轻松地将其放在外面，它仍然是您模块的私有函数：

var AuthHmac = AuthHmac || (function(_, CryptoJS) {

    function normalize(s) { return s.toLowerCase(); }

    function AuthHmac(options) {
        var options = options || {};

        this.additionalHeaders = options.additionalHeaders || {};
    };

    AuthHmac.prototype.prepare = function(request) {
        request.headers = request.headers || {};

        _.each(this.additionalHeaders, function(value, name) {
            request.headers[normalize(name)] = value;
//                          ^^^^^^^^^
//    No `this.`! "private attributes" in JS are variables, not properties
        });
    };

    return AuthHmac;

})(_, CryptoJS);

Answer 2

var AuthHmac = AuthHmac || (function(_, CryptoJS) {

function normalize(s) { return s.toLowerCase(); }

function AuthHmac(options) {
    var options = options || {};

    this.additionalHeaders = options.additionalHeaders || {};
};

AuthHmac.prototype.prepare = function(request) {
    request.headers = request.headers || {};

    _.each(this.additionalHeaders, function(value, name) {
        request.headers[normalize(name)] = value;
    });
};

return AuthHmac;

})(_, CryptoJS);

Answer 3

你不能。 JavaScript没有任何私有或公共属性的概念，因此人们使用闭包和范围作为＆＃34; hack＆＃34;模拟隐私。但这是有代价的，即原型方法无法访问这些＆＃34;私有＆＃34;属性。

在您的具体示例中，normalize也可以在构造函数之外定义，因为它不依赖于构造函数内的任何内容：

var AuthHmac = AuthHmac || (function(_, CryptoJS) {

    var normalize = function(s) { return s.toLowerCase(); };

    function AuthHmac(options) {
        var options = options || {};
        this.additionalHeaders = options.additionalHeaders || {};
    };

    AuthHmac.prototype.prepare = function(request) {
        request.headers = request.headers || {};

        _.each(this.additionalHeaders, function(value, name) {
            request.headers[normalize(name)] = value;
        });
    };

    return AuthHmac;

})(_, CryptoJS);

Answer 4

将normalise函数定义为作用域内的命名函数，而不是将其放在对象的属性中：

var AuthHmac = AuthHmac || (function(_, CryptoJS) {

  function normalize(s) {
    return s.toLowerCase();
  }

  function AuthHmac(options) {
    var options = options || {};

    this.additionalHeaders = options.additionalHeaders || {};
  };

  AuthHmac.prototype.prepare = function(request) {
    request.headers = request.headers || {};

    _.each(this.additionalHeaders, function(value, name) {
        request.headers[normalize(name)] = value;
    });
  };

  return AuthHmac;

})(_, CryptoJS);

我可以在JavaScript中的原型函数中使用私有方法吗？

4 个答案: