Douglas Crockford的"Javascript:The Good Parts"第5.5章

Question

我正在阅读书中的第5.5章.我仍然难以看到"我们可以使用章节中的可能性函数来组合各组件中的对象".

对象是由具有"on"和"fire"功能的事件系统组成的吗？

以下部分的代码:

var eventuality = function (that) {
    var registry = {};
    that.fire = function (event) {
// Fire an event on an object. The event can be either
// a string containing the name of the event or an
// object containing a type property containing the
// name of the event. Handlers registered by the 'on'
// method that match the event name will be invoked.
        var array,
            func,
            handler,
            i,
            type = typeof event === 'string' ?
                    event : event.type;
// If an array of handlers exist for this event, then
// loop through it and execute the handlers in order.
        if (registry.hasOwnProperty(type)) {
            array = registry[type];
            for (i = 0; i < array.length; i += 1) {
                handler = array[i];
// A handler record contains a method and an optional
// array of parameters. If the method is a name, look
// up the function.
                func = handler.method;
                if (typeof func === 'string') {
                    func = this[func];
                }
// Invoke a handler. If the record contained
// parameters, then pass them. Otherwise, pass the
// event object.
                func.apply(this,
                    handler.parameters || [event]);
            }
        }
        return this;
    };
    that.on = function (type, method, parameters) {
// Register an event. Make a handler record. Put it
// in a handler array, making one if it doesn't yet
// exist for this type.
        var handler = {
            method: method,
            parameters: parameters
        };
        if (registry.hasOwnProperty(type)) {
            registry[type].push(handler);
        } else {
            registry[type] = [handler];
        }
        return this;
    };
    return that;
}

Answer 1

克罗克福德什么意思先生在这里是可以实现特定功能,如on并fire通过调用创建它们(函数对象事件处理添加到任何物体的功能eventuality与对象作为参数,在这种情况下).

这里的"部分"是体现在eventuality功能对象中的"事件处理部分" .您可以想象添加其他功能的不同部分.这里的想法是您可以使用此系统将此功能添加到您需要的单个对象.这个概念称为Mixin(1).

另请阅读第5章的最后一段:

通过这种方式,构造函数可以从一组零件组装对象.JavaScript的松散输入在这里是一个很大的好处,因为我们不会担心关注类的谱系的类型系统.

(1)谢谢Zecc.