[help] Selection.setSelection()

Hi!
I have several input fields with default values, how can I select them(values) when I’m pressing on the text field?

for example input field with instance name “user_name” and default value “enter your name”

user_name.onSetFocus = function() {
    Selection.setFocus(this);
    Selection.setSelection();
}

but it didn’t work for me :frowning: