function insertNum(num1,num2,cb){
  return cb(num1,num2);
}

function sumCallback(num1,num2){
  return num1 + num2;
}

function subtraction(num1, num2){
  return num1 - num2;
}

function multiply(num1, num2){
  return num1 * num2;
}

function div(num1,num2){
  return num1 / num2;
}

function mod(num1, num2){
  return num1 % num2;
}

var ari = {
  sum: insertNum(1,1,sumCallback),
  sub: insertNum(1,1,subtraction),
  mul: insertNum(2,3, multiply),
  div: insertNum(2,2, div),
  mod: insertNum(18,4,mod),
}

var p = document.createElement('P');

for (var prop in ari){
  var res = document.createTextNode(ari[prop]);
  p.appendChild(res); document.getElementById('container').appendChild(p);
}