onkeypress js phone number

Hi
I will prefer use call convert JavaScript function on lost focus (i.e. on blur event of that textbox) So that after complete value entered you can format it.
See below code:

HTML:
<input type="text" id="txtPhone" />

JS Code:
var myInput = document.getElementById('txtPhone');
        myInput.addEventListener("blur", ConvertToUSPhone);
        
        function ConvertToUSPhone() {
            var newValue = myInput.value;
            var USNumber = newValue.match(/(\d{3})(\d{3})(\d{4})/);
            USNumber = "(" + USNumber[1] + ")" + USNumber[2] + "-" + USNumber[3];
            alert(USNumber);
        }

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use this plugin : https://github.com/digitalBush/jquery.maskedinput

$("#phoneID").mask("(999) 999-9999");

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<input id="phoneID" type="text" ..

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also what about HTML5 ?
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/tel

<input type="tel" pattern="([0-9]{3}) [0-9]{3}-[0-9]{4}" name="phone" />

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