使用进度事件侦听器覆盖主干同步

Question

我正在尝试覆盖 Backbone sync 函数以监听 progress 事件。但是，xhr.upload 未定义，因此下面的代码不起作用。有什么想法吗？

var Model = Backbone.Model.extend({

  ...

  sync: function(method, model, options) {
    options.beforeSend = function(xhr) {
      xhr.upload.addEventListener("progress", function(event) {
        if (event.lengthComputable) {  
          var percentComplete = event.loaded/event.total;
          console.log(percentComplete);
        }
      }, false); 
    }
    return Backbone.sync(method, model, options);
  },

  ...

});

Answer 1

以下是最终对我们有用的方法：

sync: function(method, model, options) { 
  options.beforeSend = function(xhr, settings) {
    settings.xhr = function() {          
      var xhr = $.ajaxSettings.xhr();
      xhr.upload.addEventListener("progress", function (event) {
        Math.ceil(event.loaded/event.total*100);
      }, false);
      return xhr;
    }
  }
  return Backbone.sync(method, model, options);
}