Código para hallar talla de zapatos en textfield

Script
function convertHeightCmToSizeShoe(ht) {
  var result = 0;
  if (ht >= 20 && ht <= 23.5) {
    result = 29;
  } else if (ht >= 23.6 && ht <= 25.5) {
    result = 30;
  } else if (ht >= 25.6 && ht <= 26.5) {
    result = 31;
  } else if (ht >= 26.6 && ht <= 28.5) {
    result = 32;
  } else if (ht >= 28.6 && ht <= 29.5) {
    result = 33;
  } else if (ht >= 29.6 && ht <= 31.5) {
    result = 34;
  } else if (ht >= 31.6 && ht <= 32.5) {
    result = 35;
  } else if (ht >= 32.6 && ht <= 34.5) {
    result = 36;
  } else if (ht >= 34.6 && ht <= 35.5) {
    result =