Andrea Azzola

Tips and Techniques for Lifestyle Design

POST data with JavaScript

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The HTML 4.0 specs

  • If the method is "get" - -, the user agent takes the value of action, appends a ? to it, then appends the form data set, encoded using the application/x-www-form-urlencoded content type. The user agent then traverses the link to this URI. In this scenario, form data are restricted to ASCII codes.
  • If the method is "post" --, the user agent conducts an HTTP post transaction using the value of the action attribute and a message created according to the content type specified by the enctype attribute.

What are the benefits of performing POSTs via JavaScript?

  • Perform redirects programmatically
  • Post data without annoying the user
  • Avoid the misuse of query string and beautify URLs

The 'post' function

Copy and paste the following code in the HEAD section of your HTML page

<script language="javascript">
function post(dictionary, url, method) {
	method = method || "post"; // post (set to default) or get

	// Create the form object
	var form = document.createElement("form");
	form.setAttribute("method", method);
	form.setAttribute("action", url);

	// For each key-value pair
	for (key in dictionary) {
		//alert('key: ' + key + ', value:' + dictionary[key]); // debug
		var hiddenField = document.createElement("input");	
		hiddenField.setAttribute("type", "hidden"); 
		hiddenField.setAttribute("name", key);
		hiddenField.setAttribute("value", dictionary[key]);
		// append the newly created control to the form

	document.body.appendChild(form); // inject the form object into the body section

How do I use it?
Copy the following code in the BODY section of your HTML page.
As you can see a dictionary object is declared as first, then two parameters are added.
You can add as many parameters as you need.

<script language="javascript">
	var myDictionary = [];
	myDictionary["1stKey"] = "1stValue";
	myDictionary["2ndKey"] = "2ndValue";

<input type="button" value="Click me to POST" 
	onclick="javascript:post(myDictionary, 'destination.html');" />
<input type="button" value="Click me to GET" 
	onclick="javascript:post(myDictionary, 'destination.html', 'get');" />

The post function accepts a dictionary object, a destination URL, and optionally, the method (post or get, case in-sensitive).

The alternative

If jQuery is already part of your solution, you may want to try the approach instead: url [, data ] [, success(data, textStatus, jqXHR) ] [, dataType ] )

which is a shorthand for the Ajax function:

  type: "POST",
  url: url,
  data: data,
  success: success,
  dataType: dataType

So, the equivalent jQuery code for POSTing the above-mentioned values would be:

$.post( "test.php", { 1stKey: "1stValue", 2ndKey: "2ndValue" } );

Further details about function can be found here