Javascript Singleton Example

singleton.js

window.AuthApi = (function(){
  var instance;

  function AuthApiObject(){
    uid = Math.random();

    return {
      foo: function(){
        console.log('foo');
      },
      bar: function(){
        console.log('bar');
      },
      id: function(){
        return uid;
      }
    }
  }

  return {
    getInstance: function(){
      if(!instance){
        instance = new AuthApiObject();
      }
      return instance;
    }
  };
})();

AuthApi.getInstance().id();
// 0.7436067988164723

AuthApi.getInstance().id();
// 0.7436067988164723

AuthApi.getInstance().id();
// 0.7436067988164723

AuthApi.getInstance().id();
// 0.7436067988164723

//shorter version

window.AuthApi = (function(){
  var uid = Math.random();

  return {
    foo: function(){
      console.log('foo');
    },
    bar: function(){
      console.log('foo');
    },
    id: function(){
      return uid;
    }
  }
})();