javascript - On propertychange issues with text value -

i have application put alert code when insert in machine 1 dollar value="" changes 1 text input shows number tried make alert on propertychange mean: when text value > = 1 shows alert telling value changed 1 or 2 3 4 show me alert when 0 , 1 want > = 1 i'm doing wrong?

basically, want show alert when value changes number bigger or equal 1

here javascript:

 <script type="text/javascript">     function init () {         var textarea = document.getelementbyid ("textarea");         if (textarea.addeventlistener) {    // firefox, opera, google chrome , safari             textarea.addeventlistener ('textinput', ontextinput, false);    // google chrome , safari         }     }          // google chrome , safari     function ontextinput (event) {         alert ("the following text has been entered: " + event.data);     }         // firefox, google chrome, opera, safari version 5     function oninput (event) {         alert ("the new content: " + event.target.value);     }         // internet explorer     function onpropchanged () {         if (event.propertyname.tolowercase () == "value>==1") {             alert ("new value on total field: " + event.srcelement.value);         }     }  </script> 

and html of form:

<td width="150" height="100"><input type="text" name="getamount" style="width:300px; height:80; text-align: left;" class="last_inp" value="" onpropertychange="$('advert_1').css('display', 'none'); onpropchanged ();"></td> 

thanks in advance

my introduce jquery?

   <input type="text" id="amount" />     <script type="text/javascript">     $(document).ready(function () {         $('#amount').change(function () {             var value = $(this).val();              if (value >= 1) {                 alert("new value on total field: " + value);             }         });     });     </script> 

some additional reading material: http://api.jquery.com/change/