Adding backdrop to side menu

custom-backdrop.js

$rootScope.$watch(function(){
   // Return ratio
   return $ionicSideMenuDelegate.getOpenRatio();
},function (ratio){
   // Broadcast the value
   $rootScope.sidemenuopened = (ratio == 1);
});

// <div ng-class="{'opaque-content' : sidemenuopened}">
// Attach to side menu content 

// Alternative CSS approach
// body.menu-open ion-side-menu-content {
//     -webkit-transition: opacity 300ms ease-in-out;
//     transition: opacity 300ms ease-in-out;
//     opacity: 0.5;
// }