如何从匿名函数访问对象实例

Question

I am dealing with the following situation.

I have to use a method from the class, but I have to call a callback too... Look at the code, I have created the _this var because I don't know how to access the DeviceAnalyzer instance from inside the anonymous function...

Is there another way? I think the way I did it is kind of nasty haha

DeviceAnalyzer.prototype.pingProcess = function(deviceInfo, callback) {
    var _this = this;
    netutils.ping(host.ipAddress, function(isAlive) {
        deviceInfo.isAlive = isAlive
        _this.emit('device', deviceInfo);
        callback(null, deviceInfo);
    });
};

Answer 1

With ES6 and anonymous function you do not have to set this or bind it.

DeviceAnalyzer.prototype.pingProcess = function(deviceInfo, callback)    {
  netutils.ping(host.ipAddress, (isAlive) => {
      deviceInfo.isAlive = isAlive
      this.emit('device', deviceInfo);
      callback(null, deviceInfo);
  });
};

Answer 2

With IIFE

DeviceAnalyzer.prototype.pingProcess = function(deviceInfo, callback) {
    (function (that) {
      return netutils.ping(host.ipAddress, function(isAlive) {
        deviceInfo.isAlive = isAlive
        that.emit('device', deviceInfo);
        callback(null, deviceInfo);
    }))(this);
};

Answer 3

The above approach is fine.

An alternative would be to use bind

DeviceAnalyzer.prototype.pingProcess = function(deviceInfo, callback) {
    netutils.ping(host.ipAddress, function(isAlive) {
        deviceInfo.isAlive = isAlive
        this.emit('device', deviceInfo);
        callback(null, deviceInfo);
    }.bind(this));
};