How to remove "undefined" from blank text boxes ？

Gantt
#1

When I click on the textbox to activate it to enterable mode，

will be automatically filled with a word “undefined”.

How to cancel this autofill ？

#2

Hello,
It happens because the value is undefined, so Gantt tries to convert it to the text type. You can modify it in the onBeforeEditStart event and replace that value with the '':

gantt.ext.inlineEditors.attachEvent("onBeforeEditStart", function(state){
  if (state.columnName == 'custom_property') {
    var task = gantt.getTask(state.id);
    if (task.custom_property == undefined) {
      task.custom_property = '';
      gantt.updateTask(task.id);
    }
  }
  return true;
});

In the following snippet, you can see how it works:
http://snippet.dhtmlx.com/5/ede328e1c

#3

It works ! thanks !!!