JavaScript post request like a form submit


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.

Dynamically create <input>s in a form and submit it

/**
 * sends a request to the specified url from a form. this will change the window location.
 * @param {string} path the path to send the post request to
 * @param {object} params the paramiters to add to the url
 * @param {string} [method=post] the method to use on the form
 */

function post(path, params, method='post') {

  // The rest of this code assumes you are not using a library.
  // It can be made less wordy if you use one.
  const form = document.createElement('form');
  form.method = method;
  form.action = path;

  for (const key in params) {
    if (params.hasOwnProperty(key)) {
      const hiddenField = document.createElement('input');
      hiddenField.type = 'hidden';
      hiddenField.name = key;
      hiddenField.value = params[key];

      form.appendChild(hiddenField);
    }
  }

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

Example:

post('/contact/', {name: 'Johnny Bravo'});

EDIT: Since this has gotten upvoted so much, I'm guessing people will be copy-pasting this a lot. So I added the hasOwnProperty check to fix any inadvertent bugs.


This would be a version of the selected answer using jQuery.

// Post to the provided URL with the specified parameters.
function post(path, parameters) {
    var form = $('<form></form>');

    form.attr("method", "post");
    form.attr("action", path);

    $.each(parameters, function(key, value) {
        var field = $('<input></input>');

        field.attr("type", "hidden");
        field.attr("name", key);
        field.attr("value", value);

        form.append(field);
    });

    // The form needs to be a part of the document in
    // order for us to be able to submit it.
    $(document.body).append(form);
    form.submit();
}

A simple quick-and-dirty implementation of @Aaron answer:

document.body.innerHTML += '<form id="dynForm" action="http://example.com/" method="post"><input type="hidden" name="q" value="a"></form>';
document.getElementById("dynForm").submit();

Of course, you should rather use a JavaScript framework such as Prototype or jQuery...


Using the createElement function provided in this answer, which is necessary due to IE's brokenness with the name attribute on elements created normally with document.createElement:

function postToURL(url, values) {
    values = values || {};

    var form = createElement("form", {action: url,
                                      method: "POST",
                                      style: "display: none"});
    for (var property in values) {
        if (values.hasOwnProperty(property)) {
            var value = values[property];
            if (value instanceof Array) {
                for (var i = 0, l = value.length; i < l; i++) {
                    form.appendChild(createElement("input", {type: "hidden",
                                                             name: property,
                                                             value: value[i]}));
                }
            }
            else {
                form.appendChild(createElement("input", {type: "hidden",
                                                         name: property,
                                                         value: value}));
            }
        }
    }
    document.body.appendChild(form);
    form.submit();
    document.body.removeChild(form);
}

Rakesh Pai's answer is amazing, but there is an issue that occurs for me (in Safari) when I try to post a form with a field called submit. For example, post_to_url("http://google.com/",{ submit: "submit" } );. I have patched the function slightly to walk around this variable space collision.

    function post_to_url(path, params, method) {
        method = method || "post";

        var form = document.createElement("form");

        //Move the submit function to another variable
        //so that it doesn't get overwritten.
        form._submit_function_ = form.submit;

        form.setAttribute("method", method);
        form.setAttribute("action", path);

        for(var key in params) {
            var hiddenField = document.createElement("input");
            hiddenField.setAttribute("type", "hidden");
            hiddenField.setAttribute("name", key);
            hiddenField.setAttribute("value", params[key]);

            form.appendChild(hiddenField);
        }

        document.body.appendChild(form);
        form._submit_function_(); //Call the renamed function.
    }
    post_to_url("http://google.com/", { submit: "submit" } ); //Works!

No. You can't have the JavaScript post request like a form submit.

What you can have is a form in HTML, then submit it with the JavaScript. (as explained many times on this page).

You can create the HTML yourself, you don't need JavaScript to write the HTML. That would be silly if people suggested that.

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

Your function would just configure the form the way you want it.

function postToURL(a,b,c){
   document.getElementById("ninja").action     = a;
   document.getElementById("donaldduck").name  = b;
   document.getElementById("donaldduck").value = c;
   document.getElementById("ninja").submit();
}

Then, use it like.

postToURL("http://example.com/","q","a");

But I would just leave out the function and just do.

document.getElementById('donaldduck').value = "a";
document.getElementById("ninja").submit();

Finally, the style decision goes in the ccs file.

#ninja{ 
  display:none;
}

Personally I think forms should be addressed by name but that is not important right now.


If you have Prototype installed, you can tighten up the code to generate and submit the hidden form like this:

 var form = new Element('form',
                        {method: 'post', action: 'http://example.com/'});
 form.insert(new Element('input',
                         {name: 'q', value: 'a', type: 'hidden'}));
 $(document.body).insert(form);
 form.submit();

this is the answer of rakesh, but with support for arrays (which is quite common in forms):

plain javascript:

function post_to_url(path, params, method) {
    method = method || "post"; // Set method to post by default, if not specified.

    // The rest of this code assumes you are not using a library.
    // It can be made less wordy if you use one.
    var form = document.createElement("form");
    form.setAttribute("method", method);
    form.setAttribute("action", path);

    var addField = function( key, value ){
        var hiddenField = document.createElement("input");
        hiddenField.setAttribute("type", "hidden");
        hiddenField.setAttribute("name", key);
        hiddenField.setAttribute("value", value );

        form.appendChild(hiddenField);
    }; 

    for(var key in params) {
        if(params.hasOwnProperty(key)) {
            if( params[key] instanceof Array ){
                for(var i = 0; i < params[key].length; i++){
                    addField( key, params[key][i] )
                }
            }
            else{
                addField( key, params[key] ); 
            }
        }
    }

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

oh, and here's the jquery version: (slightly different code, but boils down to the same thing)

function post_to_url(path, params, method) {
    method = method || "post"; // Set method to post by default, if not specified.

    var form = $(document.createElement( "form" ))
        .attr( {"method": method, "action": path} );

    $.each( params, function(key,value){
        $.each( value instanceof Array? value : [value], function(i,val){
            $(document.createElement("input"))
                .attr({ "type": "hidden", "name": key, "value": val })
                .appendTo( form );
        }); 
    } ); 

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

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});

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();
};

Three options here.

  1. Standard JavaScript answer: Use a framework! Most Ajax frameworks will have abstracted you an easy way to make an XMLHTTPRequest POST.

  2. Make the XMLHTTPRequest request yourself, passing post into the open method instead of get. (More information in Using POST method in XMLHTTPRequest (Ajax).)

  3. Via JavaScript, dynamically create a form, add an action, add your inputs, and submit that.


I'd go down the Ajax route as others suggested with something like:

var xmlHttpReq = false;

var self = this;
// Mozilla/Safari
if (window.XMLHttpRequest) {
    self.xmlHttpReq = new XMLHttpRequest();
}
// IE
else if (window.ActiveXObject) {
    self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}

self.xmlHttpReq.open("POST", "YourPageHere.asp", true);
self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');

self.xmlHttpReq.setRequestHeader("Content-length", QueryString.length);



self.xmlHttpReq.send("?YourQueryString=Value");

Here is how I wrote it using jQuery. Tested in Firefox and Internet Explorer.

function postToUrl(url, params, newWindow) {
    var form = $('<form>');
    form.attr('action', url);
    form.attr('method', 'POST');
    if(newWindow){ form.attr('target', '_blank'); 
  }

  var addParam = function(paramName, paramValue) {
      var input = $('<input type="hidden">');
      input.attr({ 'id':     paramName,
                 'name':   paramName,
                 'value':  paramValue });
      form.append(input);
    };

    // Params is an Array.
    if(params instanceof Array){
        for(var i=0; i<params.length; i++) {
            addParam(i, params[i]);
        }
    }

    // Params is an Associative array or Object.
    if(params instanceof Object) {
        for(var key in params){
            addParam(key, params[key]);
        }
    }

    // Submit the form, then remove it from the page
    form.appendTo(document.body);
    form.submit();
    form.remove();
}

The easiest way is using Ajax Post Request:

$.ajax({
    type: "POST",
    url: 'http://www.myrestserver.com/api',
    data: data,
    success: success,
    dataType: dataType
    });

where:

  • data is an object
  • dataType is the data expected by the server (xml, json, script, text, html)
  • url is the address of your RESt server or any function on the server side that accept the HTTP-POST.

Then in the success handler redirect the browser with something like window.location.


The Prototype library includes a Hashtable object, with a ".toQueryString()" method, which allows you to easily turn a JavaScript object/structure into a query-string style string. Since the post requires the "body" of the request to be a query-string formatted string, this allows your Ajax request to work properly as a post. Here's an example using Prototype:

$req = new Ajax.Request("http://foo.com/bar.php",{
    method: 'post',
    parameters: $H({
        name: 'Diodeus',
        question: 'JavaScript posts a request like a form request',
        ...
    }).toQueryString();
};

This works perfectly in my case:

document.getElementById("form1").submit();

You can use it in function like:

function formSubmit() {
     document.getElementById("frmUserList").submit();
} 

Using this you can post all the values of inputs.


My solution will encode deeply nested objects, unlike the currently accepted solution by @RakeshPai.

It uses the 'qs' npm library and its stringify function to convert nested objects into parameters.

This code works well with a Rails back-end, although you should be able to modify it to work with whatever backend you need by modifying the options passed to stringify. Rails requires that arrayFormat be set to "brackets".

import qs from "qs"

function normalPost(url, params) {
  var form = document.createElement("form");
  form.setAttribute("method", "POST");
  form.setAttribute("action", url);

  const keyValues = qs
    .stringify(params, { arrayFormat: "brackets", encode: false })
    .split("&")
    .map(field => field.split("="));

  keyValues.forEach(field => {
    var key = field[0];
    var value = field[1];
    var hiddenField = document.createElement("input");
    hiddenField.setAttribute("type", "hidden");
    hiddenField.setAttribute("name", key);
    hiddenField.setAttribute("value", value);
    form.appendChild(hiddenField);
  });
  document.body.appendChild(form);
  form.submit();
}

Example:

normalPost("/people/new", {
      people: [
        {
          name: "Chris",
          address: "My address",
          dogs: ["Jordan", "Elephant Man", "Chicken Face"],
          information: { age: 10, height: "3 meters" }
        },
        {
          name: "Andrew",
          address: "Underworld",
          dogs: ["Doug", "Elf", "Orange"]
        },
        {
          name: "Julian",
          address: "In a hole",
          dogs: ["Please", "Help"]
        }
      ]
    });

Produces these Rails parameters:

{"authenticity_token"=>"...",
 "people"=>
  [{"name"=>"Chris", "address"=>"My address", "dogs"=>["Jordan", "Elephant Man", "Chicken Face"], "information"=>{"age"=>"10", "height"=>"3 meters"}},
   {"name"=>"Andrew", "address"=>"Underworld", "dogs"=>["Doug", "Elf", "Orange"]},
   {"name"=>"Julian", "address"=>"In a hole", "dogs"=>["Please", "Help"]}]}

FormObject is an option. But FormObject is not supported by most browsers now.


Yet another recursive solution, since some of others seem to be broken (I didn't test all of them). This one depends on lodash 3.x and ES6 (jQuery not required):

function createHiddenInput(name, value) {
    let input = document.createElement('input');
    input.setAttribute('type','hidden');
    input.setAttribute('name',name);
    input.setAttribute('value',value);
    return input;
}

function appendInput(form, name, value) {
    if(_.isArray(value)) {
        _.each(value, (v,i) => {
            appendInput(form, `${name}[${i}]`, v);
        });
    } else if(_.isObject(value)) {
        _.forOwn(value, (v,p) => {
            appendInput(form, `${name}[${p}]`, v);
        });
    } else {
        form.appendChild(createHiddenInput(name, value));
    }
}

function postToUrl(url, data) {
    let form = document.createElement('form');
    form.setAttribute('method', 'post');
    form.setAttribute('action', url);

    _.forOwn(data, (value, name) => {
        appendInput(form, name, value);
    });

    form.submit();
}

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);

This is based on beauSD's code using jQuery. It is improved so it works recursively on objects.

function post(url, params, urlEncoded, newWindow) {
    var form = $('<form />').hide();
    form.attr('action', url)
        .attr('method', 'POST')
        .attr('enctype', urlEncoded ? 'application/x-www-form-urlencoded' : 'multipart/form-data');
    if(newWindow) form.attr('target', '_blank');

    function addParam(name, value, parent) {
        var fullname = (parent.length > 0 ? (parent + '[' + name + ']') : name);
        if(value instanceof Object) {
            for(var i in value) {
                addParam(i, value[i], fullname);
            }
        }
        else $('<input type="hidden" />').attr({name: fullname, value: value}).appendTo(form);
    };

    addParam('', params, '');

    $('body').append(form);
    form.submit();
}

You could dynamically add the form using DHTML and then submit.


You could use a library like jQuery and its $.post method.


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>

The method I use to post and direct a user automatically to another page is to just write a hidden form and then auto submit it. Be assured that the hidden form takes absolutely no space on the web page. The code would be something like this:

    <form name="form1" method="post" action="somepage.php">
    <input name="fielda" type="text" id="fielda" type="hidden">

    <textarea name="fieldb" id="fieldb" cols="" rows="" style="display:none"></textarea>
</form>
    document.getElementById('fielda').value="some text for field a";
    document.getElementById('fieldb').innerHTML="some text for multiline fieldb";
    form1.submit();

Application of auto submit

An application of an auto submit would be directing form values that the user automatically put in on the other page back to that page. Such an application would be like this:

fieldapost=<?php echo $_post['fielda'];>
if (fieldapost !="") {
document.write("<form name='form1' method='post' action='previouspage.php'>
  <input name='fielda' type='text' id='fielda' type='hidden'>
</form>");
document.getElementById('fielda').value=fieldapost;
form1.submit();
}

Here is how I do it.

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

        for(var key in data){
            var input = document.createElement('input');
            input.name = key;
            input.value = data[key];
            input.type = 'hidden';
            form.appendChild(input)
        }
        document.body.appendChild(form);
        form.submit();
    }

None of the above solutions handled deep nested params with just jQuery, so here is my two cents solution.

If you're using jQuery and you need to handle deep nested parameters, you can use this function below:

    /**
     * Original code found here: https://github.com/mgalante/jquery.redirect/blob/master/jquery.redirect.js
     * I just simplified it for my own taste.
     */
    function postForm(parameters, url) {

        // generally we post the form with a blank action attribute
        if ('undefined' === typeof url) {
            url = '';
        }


        //----------------------------------------
        // SOME HELPER FUNCTIONS
        //----------------------------------------
        var getForm = function (url, values) {

            values = removeNulls(values);

            var form = $('<form>')
                .attr("method", 'POST')
                .attr("action", url);

            iterateValues(values, [], form, null);
            return form;
        };

        var removeNulls = function (values) {
            var propNames = Object.getOwnPropertyNames(values);
            for (var i = 0; i < propNames.length; i++) {
                var propName = propNames[i];
                if (values[propName] === null || values[propName] === undefined) {
                    delete values[propName];
                } else if (typeof values[propName] === 'object') {
                    values[propName] = removeNulls(values[propName]);
                } else if (values[propName].length < 1) {
                    delete values[propName];
                }
            }
            return values;
        };

        var iterateValues = function (values, parent, form, isArray) {
            var i, iterateParent = [];
            Object.keys(values).forEach(function (i) {
                if (typeof values[i] === "object") {
                    iterateParent = parent.slice();
                    iterateParent.push(i);
                    iterateValues(values[i], iterateParent, form, Array.isArray(values[i]));
                } else {
                    form.append(getInput(i, values[i], parent, isArray));
                }
            });
        };

        var getInput = function (name, value, parent, array) {
            var parentString;
            if (parent.length > 0) {
                parentString = parent[0];
                var i;
                for (i = 1; i < parent.length; i += 1) {
                    parentString += "[" + parent[i] + "]";
                }

                if (array) {
                    name = parentString + "[" + name + "]";
                } else {
                    name = parentString + "[" + name + "]";
                }
            }

            return $("<input>").attr("type", "hidden")
                .attr("name", name)
                .attr("value", value);
        };


        //----------------------------------------
        // NOW THE SYNOPSIS
        //----------------------------------------
        var generatedForm = getForm(url, parameters);

        $('body').append(generatedForm);
        generatedForm.submit();
        generatedForm.remove();
    }

Here is an example of how to use it. The html code:

<button id="testButton">Button</button>

<script>
    $(document).ready(function () {
        $("#testButton").click(function () {
            postForm({
                csrf_token: "abcd",
                rows: [
                    {
                        user_id: 1,
                        permission_group_id: 1
                    },
                    {
                        user_id: 1,
                        permission_group_id: 2
                    }
                ],
                object: {
                    apple: {
                        color: "red",
                        age: "23 days",
                        types: [
                            "golden",
                            "opal",
                        ]
                    }
                },
                the_null: null, // this will be dropped, like non-checked checkboxes are dropped
            });
        });
    });
</script>

And if you click the test button, it will post the form and you will get the following values in POST:

array(3) {
  ["csrf_token"] => string(4) "abcd"
  ["rows"] => array(2) {
    [0] => array(2) {
      ["user_id"] => string(1) "1"
      ["permission_group_id"] => string(1) "1"
    }
    [1] => array(2) {
      ["user_id"] => string(1) "1"
      ["permission_group_id"] => string(1) "2"
    }
  }
  ["object"] => array(1) {
    ["apple"] => array(3) {
      ["color"] => string(3) "red"
      ["age"] => string(7) "23 days"
      ["types"] => array(2) {
        [0] => string(6) "golden"
        [1] => string(4) "opal"
      }
    }
  }
}

Note: if you want to post the form to another url than the current page, you can specify the url as the second argument of the postForm function.

So for instance (to re-use your example):

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

Hope this helps.

Note2: the code was taken from the redirect plugin. I basically just simplified it for my needs.


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'});

You could use jQuery's trigger method to submit the form, just like you press a button, like so,

$('form').trigger('submit')

it will submit on the browser.


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.


Try

function post_to_url(url, obj) {
  let id=`form_${+new Date()}`;
  document.body.innerHTML+=`
    <form id="${id}" action="${url}" method="POST">
      ${Object.keys(obj).map(k=>`
        <input type="hidden" name="${k}" value="${obj[k]}">
      `)}
    </form>`
  this[id].submit();  
}

// TEST - in second param object can have more keys
function jump() { post_to_url('https://example.com/', {'q':'a'}); }
Open chrome>networks and push button:
<button onclick="jump()">Send POST</button>