Two scenarios for the js singleton pattern

Scenario 1: you can flexibly read internal variables by taking advantage of the two functions of closures, and you can keep them in memory.

//Plan a
    var SingletonTester = (function () { 
        //Singleton method
        function Singleton(args) { 
            var args = args || {}; 
            this.name = 'SingletonTester'; //The other way is to return an object
            this.pointX = args.pointX || 6; 
            this.pointY = args.pointY || 10; 
        } 

        //The singleton instance
        var instance; 

        //Returns the object
        return { 
            name: 'SingletonTester', 

            getInstance: function (args) { 
                if (instance === undefined) { 
                    instance = new Singleton(args); 
                } 
                return instance; 
            } 
        }; 
    })(); //Execute the method directly

    // test  
    var test = SingletonTester.getInstance({ pointX: 5 }); 
    console.log(test.pointX); 

Scheme 2:

//Scheme 2
  function Universe() { 
      //Determine if an instance exists
      if (typeof Universe.instance === 'object') { 
          return Universe.instance; 
      } 

      //Other content
      this.start_time = 0; 
      this.bang = "Big"; 

      //  The cache  
      Universe.instance = this; 

      //Implicitly returns this
  } 

  //  test  
  var uni = new Universe(); 
  var uni2 = new Universe(); 
  console.log(uni === uni2); // true