JSFiddle - React, Tailwind, and code Playground

HTML

<input id="input_4" class="form-textbox" maxlength="15" name="atn" size="25" onKeyup='addDashes(this)' />

JavaScript

window.addDashes = function addDashes(f) {
    var r = /(\D+)/g,
        npa = '',
        nxx = '',
        last4 = '';
    f.value = f.value.replace(r, '');
    npa = f.value.substr(0, 3);
    nxx = f.value.substr(3, 3);
    last4 = f.value.substr(6, 4);
    f.value = npa + '-' + nxx + '-' + last4;
}