show text field on select other from drop down :ROR

How I should do this using javascript? I looked other places but e开发者_JAVA技巧very example uses Jquery.

Only on select other textbox should visible.

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Assuming that you are on an older version of rails which has prototype as the js library.

in the onchange event of the select list add the javascript function to show the div containing the text box (let's say you show the text box for value 5 of the select list):

<select id="select_item" name="select_item" onchange="display_date_range(this);">
... where 5 is the value of the option that needs to show text box
</select>

  function display_date_range(list) {
    if(list.options[list.selectedIndex].value == 5) {
      $("text_div").show();
    }
    else {
      $("text_div").hide();
    }
  }

<div id="text_div"><input type="text" value="Hooraaahhh..." /></div>