Обработать ответ сервера

function submitForm (oFormElement) { 
	var xhr = new XMLHttpRequest(); 
	xhr.onload = function() { 
		alert (xhr.responseText);  
	} 
	xhr.open (oFormElement.method, oFormElement.action, true); 
	xhr.send (new FormData (oFormElement)); 
	return false; 
}

<form name = "sign" method="POST" action="http://someurl" onsubmit="submitForm(document.forms.sign);"> 
			<p class = "username"> 
			 
				<input type="text" name="name" placeholder="Name" required="required" pattern="[a-zA-Z]+"> 
			</p> 
 
			<p class = "username"> 
 
				<input type="text" name="secondname" placeholder="Second Name" required="required" pattern="[a-zA-Z]+"> 
			</p> 
 
			<p class = "email"> 
				 
				<input type="email" name="email" placeholder="Email" required="required"> 
			</p> 
 
			<p class = "gender"> 
				<select name = "gender" required="required"> 
					<option value = "">Select your gender</option> 
					<option value = "male">Male</option> 
					<option value = "female">Female</option> 
				</select> 
			</p> 
 
			<p class = "password"> 
		 
				<input type="password" name="pass" placeholder="Password" required="required"> 
			</p> 
 
			<p class = "checkbox"> 
				<input type="checkbox" name="check" id = "checker"> 
				<span>Conditions of Agreement</span> 
				 
			</p> 
 
			<p class = "submit"> 
					<input type="submit" id = "sent" name = "Sent" disabled="true" > 
			</p> 
		</form>