Answers for "how to disable selection on dropdown menu js"

disable option dropdown jquery

//disable by value
$("#ddlList option[value='jquery']").attr("disabled","disabled");

//disable by text
$('#ddlList option:contains("HTML")').attr("disabled","disabled");

howt to disable a select tag using js

document.getElementById("one").onchange = function () {
  document.getElementById("two").setAttribute("disabled", "disabled");
  if (this.value == 'car')
    document.getElementById("two").removeAttribute("disabled");
};