这两个构造函数模式有什么区别？ [英] What is the difference between these two constructor patterns?

问题描述

Function ConstrA () {
    EventEmitter.call(this);
}
util.inherits(ConstrA, EventEmitter);

vs

Function ConstrA() {}
util.inherits(ConstrA, EventEmitter);

是否有EventEmitter.call（this）需要的东西？

Is there something that the EventEmitter.call(this) does that is required?

推荐答案

是否有EventEmitter.call（this）需要的东西？

Is there something that the EventEmitter.call(this) does that is required?

显然，是的：

function EventEmitter() {
  EventEmitter.init.call(this);
}
…

EventEmitter.init = function() {
  this.domain = null;
  if (EventEmitter.usingDomains) {
    // if there is an active domain, then attach to it.
    domain = domain || require('domain');
    if (domain.active && !(this instanceof domain.Domain)) {
      this.domain = domain.active;
    }
  }
  this._events = this._events || {};
  this._maxListeners = this._maxListeners || undefined;
};

$ b <做一个检查它的存在我不会指望太多打破，如果你省略了电话，但我不知道这是否适用于未来。

Since all the methods that use ._events do a check for its existence I wouldn't expect much to break if you did omit the call, but I'm not sure whether this holds true in the future.

还有足够的其他构造函数不允许被忽略，所以最好在构建实例时简单地 调用构造函数。

There are enough other constructors that do not tolerate to be omitted, so it's good practice to simply always call the constructor when constructing an instance.

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