Simple ajax form using javascript no jQuery

Question

I\'m working with a form for which the mark-up I can\'t change & can\'t use jQuery. Currently the form post the results to a new window. Is it possible to change this to

Answer 1

Expanding on Madara's answer: I had to make some changes to make it work on Chrome 47.0.2526.80 (not tested on anything else). Hopefully this can save someone some time.

This snippet is a modification of that answer with the following changes:

• filter !el.disabled,
• check type of input before excluding !checked
• Request type to x-www-form-urlencoded

With the following result:

function ajaxSubmit(form, callback) {
    var xhr = new XMLHttpRequest();
    var params = [].filter.call(form.elements, function (el) {return !(el.type in ['checkbox', 'radio']) || el.checked;})
    .filter(function(el) { return !!el.name; }) //Nameless elements die.
    .filter(function(el) { return !el.disabled; }) //Disabled elements die.
    .map(function(el) {
        return encodeURIComponent(el.name) + '=' + encodeURIComponent(el.value);
    }).join('&'); //Then join all the strings by &
    xhr.open("POST", form.action);
    xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xhr.onload = callback.bind(xhr);
    xhr.send(params);
};

Answer 2

The following is a far more elegant solution of the other answer, more fit for modern browsers.

My reasoning is that if you need support for older browser you already most likely use a library like jQuery, and thus making this question pointless.

/**
 * Takes a form node and sends it over AJAX.
 * @param {HTMLFormElement} form - Form node to send
 * @param {function} callback - Function to handle onload. 
 *                              this variable will be bound correctly.
 */

function ajaxPost (form, callback) {
    var url = form.action,
        xhr = new XMLHttpRequest();

    //This is a bit tricky, [].fn.call(form.elements, ...) allows us to call .fn
    //on the form's elements, even though it's not an array. Effectively
    //Filtering all of the fields on the form
    var params = [].filter.call(form.elements, function(el) {
        //Allow only elements that don't have the 'checked' property
        //Or those who have it, and it's checked for them.
        return typeof(el.checked) === 'undefined' || el.checked;
        //Practically, filter out checkboxes/radios which aren't checekd.
    })
    .filter(function(el) { return !!el.name; }) //Nameless elements die.
    .filter(function(el) { return el.disabled; }) //Disabled elements die.
    .map(function(el) {
        //Map each field into a name=value string, make sure to properly escape!
        return encodeURIComponent(el.name) + '=' + encodeURIComponent(el.value);
    }).join('&'); //Then join all the strings by &

    xhr.open("POST", url);
    // Changed from application/x-form-urlencoded to application/x-form-urlencoded
    xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

    //.bind ensures that this inside of the function is the XHR object.
    xhr.onload = callback.bind(xhr); 

    //All preperations are clear, send the request!
    xhr.send(params);
}

The above is supported in all major browsers, and IE9 and above.

Answer 3

Nowadays using FormData is the easiest method. You construct it with a reference to the Form element, and it serializes everything for you.

MDN has an example of this here -- roughly:

const form = document.querySelector("#debarcode-form");
form.addEventListener("submit", e => {
    e.preventDefault();
    const fd = new FormData(form);
    const xhr = new XMLHttpRequest();
    xhr.addEventListener("load", e => {
        console.log(e.target.responseText);
    });
    xhr.addEventListener("error", e => {
        console.log(e);
    });
    xhr.open("POST", form.action);
    xhr.send(fd);
});

and if you want it as an object (JSON):

const obj = {};
[...fd.entries()].forEach(entry => obj[entry[0]] = entry[1]);

Answer 4

I just took Coomie's answer above and made it work for Radio/Checkboxes. I can't believe how simple and clear this is. With a few exceptions, I'm done using frameworks.

    var params = "";
    var form_elements = form.elements;
    for (var i = 0; i < form_elements.length; i++) 
    {
        switch(form_elements[i].type)
        {
            case "select-one":
            {
                value = form_elements[i].options[form_elements[i].selectedIndex].value;
            }break;
            case "checkbox":
            case "radio": 
            {
                if (!form_elements[i].checked)
                {
                    continue; // we don't want unchecked data
                }
                value = form_elements[i].value;
            }break;
            case "text" :
            {
                value = form_elements[i].value;                
            }break;

        }

        params += encodeURIComponent(form_elements[i].name) + "=" + encodeURIComponent(value) + "&";
    }



    var xhr = new XMLHttpRequest();    
    xhr.open('POST', "/api/some_url");
    xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');
    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4) {
            if (xhr.status == 200)
            {

                console.log("xhr.responseText");
            }
            else
            {
                console.log("Error! Status: ", xhr.status, "Text:", xhr.responseText);
            } 
        }
    };

    console.log(params);
    xhr.send(params);

Answer 5

Here's a nifty function I use to do exactly what you're trying to do:

HTML:

<form action="/cs/Satellite">...</form>
<input type="button" value="Vote now" onclick="javascript:AJAXPost(this)">

JS:

function AJAXPost(myself) {
    var elem   = myself.form.elements;
    var url    = myself.form.action;    
    var params = "";
    var value;

    for (var i = 0; i < elem.length; i++) {
        if (elem[i].tagName == "SELECT") {
            value = elem[i].options[elem[i].selectedIndex].value;
        } else {
            value = elem[i].value;                
        }
        params += elem[i].name + "=" + encodeURIComponent(value) + "&";
    }

    if (window.XMLHttpRequest) {
        // code for IE7+, Firefox, Chrome, Opera, Safari
        xmlhttp=new XMLHttpRequest();
    } else { 
        // code for IE6, IE5
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
    }

    xmlhttp.open("POST",url,false);
    xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    xmlhttp.setRequestHeader("Content-length", params.length);
    xmlhttp.setRequestHeader("Connection", "close");
    xmlhttp.send(params);

    return xmlhttp.responseText;
}

Answer 6

The strategy is to serialise the form and send the data using XHR, then do what you want with the response. There is a good set of utilities and help at Matt Krus's Ajax Toolbox and related Javascript Toolbox.

If you are just serialising the form posted, then the following will do the trick. It can easily be extended to include other form control types:

var serialiseForm = (function() {

  // Checkboxes that have already been dealt with
  var cbNames;

  // Return the value of a checkbox group if any are checked
  // Otherwise return empty string
  function getCheckboxValue(cb) {
    var buttons = cb.form[cb.name];
    if (buttons.length) {
      for (var i=0, iLen=buttons.length; i<iLen; i++) {
        if (buttons[i].checked) {
          return buttons[i].value;
        }
      }
    } else {
      if (buttons.checked) {
        return buttons.value;
      }
    }
    return '';
  }

  return function (form) {
    var element, elements = form.elements;
    var result = [];
    var type;
    var value = '';
    cbNames = {};

    for (var i=0, iLen=elements.length; i<iLen; i++) {
      element = elements[i];
      type = element.type;

      // Only named, enabled controls are successful
      // Only get radio buttons once
      if (element.name && !element.disabled && !(element.name in cbNames)) {

         if (type == 'text' || type == 'hidden') {
          value = element.value;

        } else if (type == 'radio') {
          cbNames[element.name] = element.name;
          value = getCheckboxValue(element);

        }
      }

      if (value) {
        result.push(element.name + '=' + encodeURIComponent(value));
      }
      value = '';

    }
    return '?' + result.join('&');
  }
}());