Q:

How to use modelEvents in Marionette.js

I have 2 textfields with id's source,destination. If any field value changes that corresponding model attribute will be change. I did this one using Backbone.Model and events object in Marionette.CompositeView. It's working fine.
Once any model Attribute change corresponding function will call. For this I written the following code. It's not working the problem was even one attribute changes both functions are evaluating.
model Code:
var mapModel = Backbone.Model.extend({
  defaults: {
    startPlace: "",
    endPlace: ""
  }
});

Marionette.CompositeView code:
var mapView = Marionette.CompositeView.extend({
  events: {
    "blur #source": "sAttributeSetting",
    "blur #destination": "dAttributeSetting"
  },

  dAttributeSetting: function() {
    this.model.set({"endPlace": document.getElementById(this.ui.destinationPlace).value});
  },

  sAttributeSetting: function() {
    this.model.set({"startPlace": document.getElementById(this.ui.sourcePlace).value});
  },

  modelEvents: {
    "change startPlace": "startMarkerDisplay",
    "change endPlace": "endingMarkerDisplay"
  },

  startMarkerDisplay: function() {
    alert("start");
  },

  endingMarkerDisplay: function() {
    alert("end");
  }
});

html code:
<input type="text" id="source">
<input type="text" id="destination">

creating instance for both model and view
mapModelObj = new mapModel();
var mapViewObj = new mapView({el:$('#mapDiv'), model:mapModelObj});

problems:

Initially If I enter any value in first field(source) getting 2 alert boxes("start", "end").
Initially If you enter any value in second field(destination) getting 4 alert boxes("start", "end", "start", "end")

I tried alot but I didn't understand where I am getting the problem
Can anyone help me.
Thanks

A:

modelEvents should be connected by :. Say, event of changing startPlace should be 
'change:startPlace'

If you use space you'll end with two events, not one event specific to this attribute.
Your code 'change startPlace' represents two events, one is 'change', the other is 'startPlace'. So you'll see "start","end","start","end"

