Jquery / php表单必须单击Submit Twice为什么？

I have a simple form with jquery and php

whenever someone clicks the submit button they have to click it twice

Heres my jQuery

    $('#submit_btn').on('click', function(){
      var post_data, proceed, user_email, user_message, user_name, user_phone;

      user_name = $("input[name=name]").val();
      user_email = $("input[name=email]").val();
      user_phone = $("input[name=phone]").val();
      user_message = $("textarea[name=message]").val();
      proceed = true;
      if (user_name === "") {
        $("input[name=name]").css("border-color", "red");
        proceed = false;
      }
      if (user_email === "") {
        $("input[name=email]").css("border-color", "red");
        proceed = false;
      }
      if (user_phone === "") {
        $("input[name=phone]").css("border-color", "red");
        proceed = false;
      }
      if (user_message === "") {
        $("textarea[name=message]").css("border-color", "red");
        proceed = false;
      }
      if (proceed) {
        post_data = {
          userName: user_name,
          userEmail: user_email,
          userPhone: user_phone,
          userMessage: user_message
        };
        $.post("contact_me_test.php", post_data, (function(response) {
          var output;
          if (response.type === "error") {
            output = "<div class=\"error\">" + response.text + "</div>";
          } else {
            output = "<div class=\"success\">" + response.text + "</div>";
            $('#contact-form-container').fadeOut(function(e){
              $('#form-success-message').fadeIn();
            });
            $("#contact_form input").val("");
            $("#contact_form textarea").val("");
          }
          $("#result").hide().html(output).slideDown();
        }), "json");
      }
    });

Heres my jQuery

Is there something that requires to thing to be pressed twice here? I looked around online for hours and some people were saying you need to take the validation out of it but I've tried that and i get the same results.

Everything regarding the form is working fine the only thing is that you have to click TWICE

Try with this code:

$('#submit_btn').on('click', function(evt){
  evt.preventDefault();
  ... //Rest of code 
}