type CustomType1 = string;
  type CustomType2 = string | number | boolean;
  type CustomType3 = {
    name : string,
    age : number,
    isValid : boolean
  } | [string, number, boolean];

  let user1 : CustomType3 = {
    name : 'sangmin',
    age : 26,
    isValid : true
  };
  let user2 : CustomType3 = ['sangmin', 26, true];

  function func(val : CustomType1) : CustomType2 {
    switch(val){
      case 'string' : return val.toUpperCase();
      case 'number' : return parseInt(val);
      default : return true;
    }
  }