Watermark for textbox

HTML

<input type="text" id="UserSearch" />
<input type="button" id="btnClick">

JavaScript

$(document).ready(function() {
var mapObj = {
  1: 'I',
  5: 'V',
  10: 'X',
  50: 'L',
  100: 'C',
  500: 'D',
  1000: 'M'
},
inputNumber = 15,
maxLimit = 3000,
temp = '';

//absolute
function getLimiter () {
    var firstLimitter, lastLimitter;
    for(var x in mapObj) {
      if (inputNumber >= x) {
        firstLimitter = x;
      } else {
        lastLimitter = x;return;
      }
    }
    return firstLimitter;
}

$("#btnClick").on("click", function() {
	getRomanNumber();
});
function getRomanNumber() {
  var limiter;
  if(mapObj[inputNumber]) {
    return mapObj[inputNumber];
  } else {
      limiter = getLimiter();
      $('#UserSearch').val(limiter);
      return limiter;
  }
}


});