anti3.js

function student(...args){

  const inputArray = args // [ 'hello', 'world', 'people' ]

  this.fname = inputArray[0];
  if (inputArray.length === 3) {
    this.mname = inputArray[1];
    this.lname = inputArray[2];
  } else {
    this.mname = '';
    this.lname = inputArray[1];
  }

  this.getFullName = function (){
      return this.fname + " " + this.mname + " " + this.lname;
   }
}


console.log(new student('gp', 'geonpyung', 'lee').getFullName()) // gp geonpyung lee

console.log(new student('gp', 'lee').getFullName()) // gp lee