问使用Javascript或jQuery从表单字段构建URL？

<form id="form1" name="form1" method="post" action="">
  <p>
    <label>Variable 1
      <input type="text" name="variable1" id="variable1" />
    </label>
  </p>
  <p>
    <label>Variable 2
      <input type="text" name="variable2" id="variable2" />
    </label>
  </p>
  <p>
    <label>URL
      <input type="text" name="url" id="url" />
    </label>
  </p>
  <p>
    <input type="submit" name="button" id="button" value="Submit" />
  </p>
</form>