了解Javascript中的單例對象

Question

我無法理解實例調用new Universe（）時會發生什么。 它不只是返回“ undefined”嗎？

function Universe() {
  var instance;

  Universe = function Universe() {
    return instance;
  }

  Universe.prototype = this;
  instance = new Universe();
  instance.constructor = Universe;
  instance.start_time = 0;
  instance.bang = "big";
  return instance;
}

Answer 1

它不會返回undefined而不是它將返回object。請參見警報框或控制台；

 function Universe() {
          var instance;

          Universe = function Universe() {
            return instance;
          }

          Universe.prototype = this;
          instance = new Universe();
          alert("ins"+instance);//or
       console.log(instance);
          instance.constructor = Universe;
          instance.start_time = 0;
          instance.bang = "big";
          return instance;
        }

        alert(Universe());//or
console.log(Universe());