Phone Number Format TextField Automatically (AS3)

formatPhoneNum.as3

var phoneField:TextField = new TextField();
with (phoneField) {
    type=TextFieldType.INPUT;
    maxChars=12;
    restrict="0-9";
    border=true;
    width=100;
    height=20;
    x=y=20;
}
addChild(phoneField);
 
phoneField.addEventListener(TextEvent.TEXT_INPUT, onInput);
 
function onInput(evt:TextEvent):void {
    if (phoneField.length==3 || phoneField.length==7) {
        phoneField.appendText("-");
        var leng:int=phoneField.text.length;
        phoneField.setSelection(leng, leng);
    }
}