<form id="login-form" method="post" onsubmit="return checkForm()"> 輸入密碼<input type="password" id="input-password"> <input type="hidden" id="md5-password" name="password"> <button type="submit">Submit</button></form>

function checkForm() { var input_pwd = document.getElementById('input-password'); var md5_pwd = document.getElementById('md5-password'); // 把用戶輸入的明文變為MD5: md5_pwd.value = toMD5(input_pwd.value); // 繼續下一步: return true;}