Answers for "on change writing textarea jquery"

jquery detect change in textarea content

$('#textareaID').bind('input propertychange', function() {

      $("#yourBtnID").hide();

      if(this.value.length){
        $("#yourBtnID").show();
      }
});

append textarea jquery with value

var $edit = $("#edit");
var curValue = $edit.val();
var newValue = curValue + "whatever new stuff here";
$edit.val(newValue);