window.onload方法，如何调用多个函数

编写一些JavaScript，使表单不会在填写的字段较少的情况下提交，如果用户未填写，则会弹出一条消息，提示“请填写名称字段”或“请填写电子邮件字段”等。我正在为每个字段编写一个单独的函数（不知道这是否是正确的方法），当我将每个函数添加到window.onload时，它只会弹出其中一条消息。任何建议都很好。

的HTML

 <form id="frmContact" name="frmContact" method="post" action="thanks.htm">
    <fieldset id="quickSupport">
      <legend><strong>Quick Support</strong></legend>
      <p> If your request isn't urgent, drop us a quick line and we'll get back to you within 24 hours </p>
      <p>
        <label for="name">Name:</label>
        <input type="text" value="Your Name" name="name" id="name" tabindex="10" />
      </p>
      <p>
        <label for="email">Email:</label>
        <input type="text" value="Your Email" name="email" id="email" tabindex="20" />
      </p>
        <label for="comments">Comments </label>
        <br />
        <textarea name="comments" value="Message" id="comments" cols="45" rows="5" tabindex="60" onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;">Message</textarea>
      </p>
      <p>
        <input type="submit" name="submit" id="submit" value="Send" tabindex="70" />
      </p>
    </fieldset>
  </form>

   <p><span id="errorMessage"></span></p>
   <p><span id="errorMessage1"></span></p>

的JavaScript

function prepareEventHandlers () {
document.getElementById("frmContact").addEventListener("submit", function(event) {

        // Show message
        if (document.getElementById("email").value == "Your Email") {
            document.getElementById("errorMessage").innerHTML = "Please provide at least an email address!";
            // to STOP the form from submitting
            return false;
        } else {
            // reset and allow the form to submit
            document.getElementById("errorMessage").innerHTML = "";
            return true;
        }

        event.preventDefault(); // Prevent form from submitting
    }
});
}

function prepareEventHandlersName () {
document.getElementById("frmContact").addEventListener("submit",         function(event) {

        // Show message
        if (document.getElementById("name").value == "Your Name") {
            document.getElementById("errorMessage1").innerHTML = "Please provide a name!";
            // to STOP the form from submitting
            return false;
        } else {
            // reset and allow the form to submit
            document.getElementById("errorMessage1").innerHTML = "";
            return true;
        }

        event.preventDefault(); // Prevent form from submitting
    }
});
}


function start() {
prepareEventHandlers();
prepareEventHandlersName();
}

window.onload =开始;