Meteor Js : How to show an animation of an engine running while processing?

For do this you can use the package :  sacha:spin

You need :

meteor add sacha:spin

And add in your layout :

{{> spinner}}

Example :

js file :

var process = new ReactiveVar("");

Template.PaymentResult.helpers({
    'isProcessing':function(){
        if ( process.get() == true){
            return true;
        } else {
            return false;
        }
    }
});

html file

   {{#if isProcessing}}
        Loading ...
        {{> spinner}}
    {{else}}
        { .... }
    {{/if}} 

+ More : https://atmospherejs.com/sacha/spin