Ember.set and Ember.setProperties

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
    name:"Vignesh",
  	place:"Nmkl",
  	
  	handleName1 : function(){
      	this.set("place","Chennai");
    }.observes("name"),
  	
  	actions:{
      	modifyTogether:function(){
            this.setProperties({name:"Vignesh Raja",place:"Namakkal"})
        },
      	
      	modifySeperately:function(){
          	this.set("name","Vignesh Raja");
          	this.set("place","Namakkal");
        }
    }
});

templates.application.hbs

Name: {{name}}<br>
Place: {{place}}<br><br>

<button {{action "modifyTogether"}}>this.setProperties({name:"Vignesh Raja",place:"Namakkal"})</button>

<br><br><br>

<button {{action "modifySeperately"}}>this.set("name","Vignesh Raja");<br>this.set("place","Namakkal");</button>

<br><br><br>

When set seperately, we get the latest value - {name:"Vignesh Raja", place:"Namakkal"}<br>
When set together, we get the latest value from the observer- {name:"Vignesh Raja", place:"Chennai"}<br>
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}