- Javascript 코드 function changePhone1(){ const phone1 = document.getElementById("phone1").value if(phone1.length === 3) { document.getElementById("phone2").focus() } } function changePhone2(){ const phone2 = document.getElementById("phone2").value if(phone2.length === 4) { document.getElementById("phone3").focus() } } function changePhone3(){ const phone1 = document.getElementById("phone1").valu..