Question

我在Mac上的Chrome中尝试此操作：

function SoundRecorder() {
}

SoundRecorder.prototype.recordSound = function() {
  navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
  if (!navigator.getUserMedia) {
    alert('Media is not supported in your browser');
    return;
  }
  navigator.getUserMedia({
    audio: true
  }, this.success, this.failure);
};

SoundRecorder.prototype.success = function(e) {
  console.log(this == window);
};

SoundRecorder.prototype.failure = function() {
  return alert('You denied permission');
};

我跑的时候 new SoundRecorder().recordSound() 它打印出真实。它的值不应该是SoundRecoder的“实例”。我错过了什么或者这是Chrome Bug？

我在Firefox中试过它，其价值是“SoundRecorder.prototype.success”

Answer 1

您可以通过对实例保持闭包，然后在调用中将其设置为 this 来设置正确的 this ：

SoundRecorder.prototype.recordSound = function() {

  // Keep reference to this, i.e. instance calling the method
  var soundRecorder = this;

  navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia ||
                           navigator.mozGetUserMedia || navigator.msGetUserMedia;
  if (!navigator.getUserMedia) {
    alert('Media is not supported in your browser');
    return;
  }

  navigator.getUserMedia({audio: true},

                         // Call the functions, setting their this to the instance
                         function() {soundRecorder.success()},
                         function() {soundRecorder.failure()}
  );
};

Bergi引用的重复答案说明了这一点。

＆＃39;这＆＃39;是getMediaUserCallback而不是Object的窗口

1 个答案: