jQuery AJAX submit form

// this is the id of the form
$("#idForm").submit(function(e) {

    e.preventDefault(); // avoid to execute the actual submit of the form.

    var form = $(this);
    var url = form.attr('action');

    $.ajax({
           type: "POST",
           url: url,
           data: form.serialize(), // serializes the form's elements.
           success: function(data)
           {
               alert(data); // show response from the php script.
           }
         });

});

$("#theForm").ajaxForm({url: 'server.php', type: 'post'})

$("#theForm").ajaxSubmit({url: 'server.php', type: 'post'})

$.get('server.php?' + $('#theForm').serialize())

$.post('server.php', $('#theForm').serialize())

<script type="text/javascript">
    var frm = $('#contactForm1');

    frm.submit(function (e) {

        e.preventDefault();

        $.ajax({
            type: frm.attr('method'),
            url: frm.attr('action'),
            data: frm.serialize(),
            success: function (data) {
                console.log('Submission was successful.');
                console.log(data);
            },
            error: function (data) {
                console.log('An error occurred.');
                console.log(data);
            },
        });
    });
</script>

$(function() {
  $('form.my_form').submit(function(event) {
    event.preventDefault(); // Prevent the form from submitting via the browser
    var form = $(this);
    $.ajax({
      type: form.attr('method'),
      url: form.attr('action'),
      data: form.serialize()
    }).done(function(data) {
      // Optionally alert the user of success here...
    }).fail(function(data) {
      // Optionally alert the user of an error here...
    });
  });
});

$(function() {
  $('form.my_form').trigger('submit');
});

(function($) {
  $.fn.autosubmit = function() {
    this.submit(function(event) {
      event.preventDefault();
      var form = $(this);
      $.ajax({
        type: form.attr('method'),
        url: form.attr('action'),
        data: form.serialize()
      }).done(function(data) {
        // Optionally alert the user of success here...
      }).fail(function(data) {
        // Optionally alert the user of an error here...
      });
    });
    return this;
  }
})(jQuery)

$(function() {
  $('form[data-autosubmit]').autosubmit();
});

var formData = new FormData(document.getElementsByName('yourForm')[0]);// yourForm: form selector        
$.ajax({
    type: "POST",
    url: "yourURL",// where you wanna post
    data: formData,
    processData: false,
    contentType: false,
    error: function(jqXHR, textStatus, errorMessage) {
        console.log(errorMessage); // Optional
    },
    success: function(data) {console.log(data)} 
});

...

<script>
    (function($){
        $("body").on("submit", ".my-form", function(e){
            e.preventDefault();
            var form = $(e.target);
            $.post( form.attr("action"), form.serialize(), function(res){
                console.log(res);
            });
        });
    )(jQuery);
</script>

jQuery(document).submit(function(e){
    var form = jQuery(e.target);
    if(form.is("#form-id")){ // check if this is the form that you want (delete this check to apply this to all forms)
        e.preventDefault();
        jQuery.ajax({
            type: "POST",
            url: form.attr("action"), 
            data: form.serialize(), // serializes the form's elements.
            success: function(data) {
                console.log(data); // show response from the php script. (use the developer toolbar console, firefox firebug or chrome inspector console)
            }
        });
    }
});

jQuery(document).click(function(e){
    var self = jQuery(e.target);
    if(self.is("#form-id input[type=submit], #form-id input[type=button], #form-id button")){
        e.preventDefault();
        var form = self.closest('form'), formdata = form.serialize();
        //add the clicked button to the form data
        if(self.attr('name')){
            formdata += (formdata!=='')? '&':'';
            formdata += self.attr('name') + '=' + ((self.is('button'))? self.html(): self.val());
        }
        jQuery.ajax({
            type: "POST",
            url: form.attr("action"), 
            data: formdata, 
            success: function(data) {
                console.log(data);
            }
        });
    }
});

if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
    //is ajax
}

$(document).on("submit", "form", function(event)
{
    event.preventDefault();        
    $.ajax({
        url: $(this).attr("action"),
        type: $(this).attr("method"),
        dataType: "JSON",
        data: new FormData(this),
        processData: false,
        contentType: false,
        success: function (data, status)
        {

        },
        error: function (xhr, desc, err)
        {

        }
    });        
});

;(function(defaults, $, undefined) {
    var getSubmitHandler = function(onsubmit, success, error) {
        return function(event) {
            if (typeof onsubmit === 'function') {
                onsubmit.call(this, event);
            }
            var form = $(this);
            $.ajax({
                type: form.attr('method'),
                url: form.attr('action'),
                data: form.serialize()
            }).done(function() {
                if (typeof success === 'function') {
                    success.apply(this, arguments);
                }
            }).fail(function() {
                if (typeof error === 'function') {
                    error.apply(this, arguments);
                }
            });
            event.preventDefault();
        };
    };
    $.fn.extend({
        // Usage:
        // jQuery(selector).ajaxForm({ 
        //                              onsubmit:function() {},
        //                              success:function() {}, 
        //                              error: function() {} 
        //                           });
        ajaxForm : function(options) {
            options = $.extend({}, defaults, options);
            return $(this).each(function() {
                $(this).submit(getSubmitHandler(options['onsubmit'], options['success'], options['error']));
            });
        }
    });
})({}, jQuery);

 $('form').ajaxForm({
      onsubmit: function(event) {
          // User submitted the form
      },
      success: function(data, textStatus, jqXHR) {
          // The form was successfully submitted
      },
      error: function(jqXHR, textStatus, errorThrown) {
          // The submit action failed
      }
 });

formSubmit('#login-form', '/api/user/login', '/members/');

function formSubmit(form, url, target) {
    $(form).submit(function(event) {
        $.post(url, $(form).serialize())
            .done(function(res) {
                if (res.success) {
                    window.location = target;
                }
                else {
                    alert(res.error);
                }
            })
            .fail(function(res) {
                alert("Server Error: " + res.status + " " + res.statusText);

            })
        event.preventDefault();
    });
}

.....

Save

$("#submitForm").submit(function(e) {
    e.preventDefault();
    var frm = $("#submitForm");
    var data = {};
    $.each(this, function(i, v){
        var input = $(v);
        data[input.attr("name")] = input.val();
        delete data["undefined"];
    });
    $.ajax({
        contentType:"application/json; charset=utf-8",
        type:frm.attr("method"),
        url:frm.attr("action"),
        dataType:'json',
        data:JSON.stringify(data),
        success:function(data) {
            alert(data.message);
        }
    });
});

$('table+table form').closest('tr').filter(':not(:last-child)').submit(function (ev, frm) {
        frm = $(ev.target).closest('form');
        $.ajax({
            type: frm.attr('method'),
            url: frm.attr('action'),
            data: frm.serialize(),
            success: function (data) {
                alert(data);
            }
        })
        ev.preventDefault();
    });

 $("#idForm").unbind().submit( function(e) {
  ....

<input id="firstName" name="firstName" ...

firstName=Chris&lastName=Halcrow ...

    <input type="text" name="name" id="name" >
    <textarea name="text" id="message" placeholder="Write something to us"> 

<script>
    function formSubmit(){
        var name = document.getElementById("name").value;
        var message = document.getElementById("message").value;
        var dataString = 'name='+ name + '&message=' + message;
        jQuery.ajax({
            url: "submit.php",
            data: dataString,
            type: "POST",
            success: function(data){
                $("#myForm").html(data);
            },
            error: function (){}
        });
    return true;
    }
</script>

var $form = $('').append(
    $('<input/>', {name: 'username'}).val('John Doe'),
    $('<input/>', {name: 'user_id'}).val('john.1234')
);

$.ajax({
    url: 'api/user/search',
    type: 'POST',
    contentType: 'application/x-www-form-urlencoded',
    data: $form.serialize(),
    success: function(data, textStatus, jqXHR) {
        console.info(data);
    },
    error: function(jqXHR, textStatus, errorThrown) {
        var errorMessage = jqXHR.responseText;
        if (errorMessage.length > 0) {
            alert(errorMessage);
        }
    }
});

const form = document.forms["orderproductForm"];
const formInputs = form.getElementsByTagName("input"); 
let formData = new FormData(); 
for (let input of formInputs) {
    formData.append(input.name, input.value); 
}

fetch(form.action,
    {
        method: form.method,
        body: formData
    })
    .then(response => response.json())
    .then(data => console.log(data))
    .catch(error => console.log(error.message))
    .finally(() => console.log("Done"));