Untitled

How to get input value on button click?
<form accept-charset="UTF-8" id="form_id" action="/" method="post">
  <input type="text" value="" placeholder="Email" name="fields_email" class="email_field">
  <input type="submit" value="Subscribe" name="Subscribe" class="subscribe_btn">
</form>

$('.subscribe_btn').click(function(e){
  e.preventDefault();
  console.log( $("#form_id .email_field").val() );
});

$('.subscribe_btn').click(function(e) {
    e.preventDefault();

    alert($("#form_id .email_field").val());

});