text: const runButton = document.getElementById("runbutton")
  runButton.addEventListener('click',check)
  
      function check(){
          
          let txtnumber = document.getElementById("txtnumber")
  
          let select_one = document.getElementById("select_one")
          let select_two = document.getElementById("select_two")
          let select_three = document.getElementById("select_three")
          let select_four = document.getElementById("select_four")
  
          if(txtnumber.value.length == 0){
              alert(`[ERROR] type any number`)
          }else{
              let num = Number(txtnumber.value)
  
              select_one.innerHTML = ``
              select_two.innerHTML = ``
              select_three.innerHTML = ``
              select_four.innerHTML = ``
  
              for(let a = 1; a <= 10; a++){
                  let option_one = document.createElement('option')
                  option_one.text = `${num} + ${a} = ${num+a}`
                  select_one.appendChild(option_one)
              }
  
  
              let b = 1
              do{
                  
                  let option_two = document.createElement('option')
                  option_two.text = `${num} - ${b} = ${num-b}`
                  select_two.appendChild(option_two)
                  b++
              }while(b <= 10)
  
  
              let c = 1
              while(c <= 10){
                  let option_three = document.createElement('option')
                  option_three.text = `${num} * ${c} = ${num*c}`
                  select_three.appendChild(option_three)
                  c++
              }
  
              for(let d = 1; d <= 10 ; d++){
                  let option_four = document.createElement('option')
                  option_four.text = `${num} / ${d} = ${num/d}`
                  select_four.appendChild(option_four)
              }
          }
      }