var input = document.getElementById('myTextInput');_x000D_
input.focus();_x000D_
input.setSelectionRange( 6, 19 );
_x000D_
<input id="myTextInput" value="Hello default value world!" />
_x000D_
select particular text on textfield
Also you can use like
input.selectionStart = 6;
input.selectionEnd = 19;