你指的是这个吗？

const setSelectGender = event => {
  const id = event.srcElement.value
  let gender = "male"
  if(id == 1) { gender = "male" }  
  if(id == 2) { gender = "female" }  

  document.querySelectorAll("#gendersSelect option")
  .forEach(opt => { opt.selected = opt.value == gender ? true : false })
}

document.querySelector("#inputNumber")
.addEventListener("change", setSelectGender)

<form>
  <input type="number" id="inputNumber">
  <select id="gendersSelect">
    <option value="male">Male</option>
    <option value="female">Female</option>
  </select>
</form>