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

VS

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

EventEmitter.call(this)是否需要这样做？

解决方法:

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

Apparently,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;
};

由于使用._events的所有方法都检查它是否存在,如果你省略了调用,我不会期望太多打破,但我不确定这是否适用于将来.

有足够的其他构造函数不能容忍被省略,因此在构造实例时简单地总是调用构造函数是一种好习惯.