Nintex Forms. JavaScript: set value to dropdown control by Text.

I need to set by JavaScript a value to a dropdown field control knowing only Text.

For example, There is a dropdown control that has 3 values - One, Two, Three. I need to set my value to Three by JavaScript. I found that aricle Custom Script on O365 and according to this I can set value only knowing Id, but I want set value not by Id but by Text.

That works:

1. NWF.FormFiller.Events.RegisterAfterReady(function () {  
2.     NWF$('#' + ddlStaff).on('change', function (e) {  
3.         if (e.originalEvent == undefined) {  
4.             if (this.value == "") {  
5.                 this.value = "1";  
6.             }  
7.         }  
8.     });  
9. });

But like this it does not work:

1. NWF.FormFiller.Events.RegisterAfterReady(function () {  
2.     NWF$('#' + ddlStaff).on('change', function (e) {  
3.         if (e.originalEvent == undefined) {  
4.             if (this.value == "") {  
5.                 this.value = "Three";  
6.             }  
7.         }  
8.     });  
9. });

Any ideas how to set value by Text?