abort()ing previous xhr requests to avoid callback race conditions

API.getJSON.js

var API = {
      getJSON: function(path, params, success){
        var that = this;
        if (_.isFunction(params)){
          success = params;
          params = null;
        }
        
        if(this.runningRequest)
          this.runningRequest.abort();
        
        this.runningRequest = $.ajax({
          url: path,
          data: params,
          complete: function(xhr, textStatus){
            that.runningRequest = null;
            if(xhr.status==200)
              success.call(that, $.parseJSON(xhr.responseText), textStatus);
          }
        });
      }
    }