在AngularJS中上传文件而无需提交按钮

在没有提交按钮的情况下提交文件时，angularjs的最佳做法是什么? 这是我的示例代码.

What is the best practices in angularjs when submitting file without a submit button. Here is my sample code.

<form method="post" enctype="multipart/form-data" action="">
   <input type="file" name="file">
</form>

我已经尝试使用onchange，它也非常有用，但是我想要的是选择文件后将进行ajax调用(没有提交按钮).

I already tried using onchange, very useful also but what i want is after selecting a file it will make an ajax call (without submit button).