JavaScript post request like a form submit

Question

I'm trying to direct a browser to a different page. If I wanted a GET request, I might say

document.location.href = 'http://example.com/q=a';

But the resource I'm trying to access won't respond properly unless I use a POST request. If this were not dynamically generated, I might use the HTML

<form action="http://example.com/" method="POST">
  <input type="hidden" name="q" value="a">
</form>

Then I would just submit the form from the DOM.

But really I would like JavaScript code that allows me to say

post_to_url('http://example.com/', {'q':'a'});

What's the best cross browser implementation?

Edit

I'm sorry I was not clear. I need a solution that changes the location of the browser, just like submitting a form. If this is possible with XMLHttpRequest, it is not obvious. And this should not be asynchronous, nor use XML, so Ajax is not the answer.

Answer 1

jQuery plugin for redirect with POST or GET:

https://github.com/mgalante/jquery.redirect/blob/master/jquery.redirect.js

To test, include the above .js file or copy/paste the class into your code, then use the code here, replacing "args" with your variable names, and "values" with the values of those respective variables:

$.redirect('demo.php', {'arg1': 'value1', 'arg2': 'value2'});

Answer 2

You could make an AJAX call (likely using a library such as using Prototype.js or JQuery). AJAX can handle both GET and POST options.

Answer 3

Well, wish I had read all the other posts so I didn't lose time creating this from Rakesh Pai's answer. Here's a recursive solution that works with arrays and objects. No dependency on jQuery.

Added a segment to handle cases where the entire form should be submitted like an array. (ie. where there's no wrapper object around a list of items)

/**
 * Posts javascript data to a url using form.submit().  
 * Note: Handles json and arrays.
 * @param {string} path - url where the data should be sent.
 * @param {string} data - data as javascript object (JSON).
 * @param {object} options -- optional attributes
 *  { 
 *    {string} method: get/post/put/etc,
 *    {string} arrayName: name to post arraylike data.  Only necessary when root data object is an array.
 *  }
 * @example postToUrl('/UpdateUser', {Order {Id: 1, FirstName: 'Sally'}});
 */
function postToUrl(path, data, options) {
    if (options === undefined) {
        options = {};
    }

    var method = options.method || "post"; // Set method to post by default if not specified.

    var form = document.createElement("form");
    form.setAttribute("method", method);
    form.setAttribute("action", path);

    function constructElements(item, parentString) {
        for (var key in item) {
            if (item.hasOwnProperty(key) && item[key] != null) {
                if (Object.prototype.toString.call(item[key]) === '[object Array]') {
                    for (var i = 0; i < item[key].length; i++) {
                        constructElements(item[key][i], parentString + key + "[" + i + "].");
                    }
                } else if (Object.prototype.toString.call(item[key]) === '[object Object]') {
                    constructElements(item[key], parentString + key + ".");
                } else {
                    var hiddenField = document.createElement("input");
                    hiddenField.setAttribute("type", "hidden");
                    hiddenField.setAttribute("name", parentString + key);
                    hiddenField.setAttribute("value", item[key]);
                    form.appendChild(hiddenField);
                }
            }
        }
    }

    //if the parent 'data' object is an array we need to treat it a little differently
    if (Object.prototype.toString.call(data) === '[object Array]') {
        if (options.arrayName === undefined) console.warn("Posting array-type to url will doubtfully work without an arrayName defined in options.");
        //loop through each array item at the parent level
        for (var i = 0; i < data.length; i++) {
            constructElements(data[i], (options.arrayName || "") + "[" + i + "].");
        }
    } else {
        //otherwise treat it normally
        constructElements(data, "");
    }

    document.body.appendChild(form);
    form.submit();
};

Answer 4

One solution is to generate the form and submit it. One implementation is

function post_to_url(url, params) {
    var form = document.createElement('form');
    form.action = url;
    form.method = 'POST';

    for (var i in params) {
        if (params.hasOwnProperty(i)) {
            var input = document.createElement('input');
            input.type = 'hidden';
            input.name = i;
            input.value = params[i];
            form.appendChild(input);
        }
    }

    form.submit();
}

So I can implement a URL shortening bookmarklet with a simple

javascript:post_to_url('http://is.gd/create.php', {'URL': location.href});

Answer 5

This is like Alan's option 2 (above). How to instantiate the httpobj is left as an excercise.

httpobj.open("POST", url, true);
httpobj.setRequestHeader('Content-Type','application/x-www-form-urlencoded; charset=UTF-8');
httpobj.onreadystatechange=handler;
httpobj.send(post);

Answer 6

I use the document.forms java and loop it to get all the elements in the form, then send via xhttp. So this is my solution for javascript / ajax submit (with all html included as an example):

          <!DOCTYPE html>
           <html>
           <body>
           <form>
       First name: <input type="text" name="fname" value="Donald"><br>
        Last name: <input type="text" name="lname" value="Duck"><br>
          Addr1: <input type="text" name="add" value="123 Pond Dr"><br>
           City: <input type="text" name="city" value="Duckopolis"><br>
      </form> 



           <button onclick="smc()">Submit</button>

                   <script>
             function smc() {
                  var http = new XMLHttpRequest();
                       var url = "yourphpfile.php";
                     var x = document.forms[0];
                          var xstr = "";
                         var ta ="";
                    var tb ="";
                var i;
               for (i = 0; i < x.length; i++) {
     if (i==0){ta = x.elements[i].name+"="+ x.elements[i].value;}else{
       tb = tb+"&"+ x.elements[i].name +"=" + x.elements[i].value;
             } }

           xstr = ta+tb;
      http.open("POST", url, true);
       http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

      http.onreadystatechange = function() {
          if(http.readyState == 4 && http.status == 200) {

        // do whatever you want to with the html output response here

                } 

               }
            http.send(xstr);

              }
         </script>

         </body>
     </html>