How to read the post request parameters using JavaScript

Question

I am trying to read the post request parameters from my HTML. I can read the get request parameters using the following code in JavaScript.

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Answer 1

It depends of what you define as JavaScript. Nowdays we actually have JS at server side programs such as NodeJS. It is exacly the same JavaScript that you code in your browser, exept as a server language. So you can do something like this: (Code by Casey Chu: https://stackoverflow.com/a/4310087/5698805)

var qs = require('querystring');

function (request, response) {
    if (request.method == 'POST') {
        var body = '';

        request.on('data', function (data) {
            body += data;

            // Too much POST data, kill the connection!
            // 1e6 === 1 * Math.pow(10, 6) === 1 * 1000000 ~~~ 1MB
            if (body.length > 1e6)
                request.connection.destroy();
        });

        request.on('end', function () {
            var post = qs.parse(body);
            // use post['blah'], etc.
        });
    }
}

And therefrom use post['key'] = newVal; etc...

Answer 2

<script>
<?php
if($_POST) { // Check to make sure params have been sent via POST
  foreach($_POST as $field => $value) { // Go through each POST param and output as JavaScript variable
    $val = json_encode($value); // Escape value
    $vars .= "var $field = $val;\n";
  }
  echo "<script>\n$vars</script>\n";
}
?>
</script>

Or use it to put them in an dictionary that a function could retrieve:

<script>
<?php
if($_POST) {
  $vars = array();
  foreach($_POST as $field => $value) {
    array_push($vars,"$field:".json_encode($value)); // Push to $vars array so we can just implode() it, escape value
  }
  echo "<script>var post = {".implode(", ",$vars)."}</script>\n"; // Implode array, javascript will interpret as dictionary
}
?>
</script>

Then in JavaScript:

var myText = post['text'];

// Or use a function instead if you want to do stuff to it first
function Post(variable) {
  // do stuff to variable before returning...
  var thisVar = post[variable];
  return thisVar;
}

This is just an example and shouldn't be used for any sensitive data like a password, etc. The POST method exists for a reason; to send data securely to the backend, so that would defeat the purpose.

But if you just need a bunch of non-sensitive form data to go to your next page without /page?blah=value&bleh=value&blahbleh=value in your url, this would make for a cleaner url and your JavaScript can immediately interact with your POST data.

Answer 3

$(function(){
    $('form').sumbit{
        $('this').serialize();
    }
});

In jQuery, the above code would give you the URL string with POST parameters in the URL. It's not impossible to extract the POST parameters.

To use jQuery, you need to include the jQuery library. Use the following for that:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.1/jquery.min.js" type="text/javascript"></script>

Answer 4

You can 'json_encode' to first encode your post variables via PHP. Then create a JS object (array) from the JSON encoded post variables. Then use a JavaScript loop to manipulate those variables... Like - in this example below - to populate an HTML form form:

<script>

    <?php $post_vars_json_encode =  json_encode($this->input->post()); ?>

    // SET POST VALUES OBJECT/ARRAY
    var post_value_Arr = <?php echo $post_vars_json_encode; ?>;// creates a JS object with your post variables
    console.log(post_value_Arr);

    // POPULATE FIELDS BASED ON POST VALUES
    for(var key in post_value_Arr){// Loop post variables array

        if(document.getElementById(key)){// Field Exists
            console.log("found post_value_Arr key form field = "+key);
            document.getElementById(key).value = post_value_Arr[key];
        }
    }


</script>

Answer 5

I have a simple code to make it:

In your index.php :

<input id="first_post_data" type="hidden" value="<?= $_POST['first_param']; ?>"/>

In your main.js :

let my_first_post_param = $("#first_post_data").val();

So when you will include main.js in index.php (<script type="text/javascript" src="./main.js"></script>) you could get the value of your hidden input which contains your post data.

Answer 6

POST variables are only available to the browser if that same browser sent them in the first place. If another website form submits via POST to another URL, the browser will not see the POST data come in.

SITE A: has a form submit to an external URL (site B) using POST SITE B: will receive the visitor but with only GET variables