jsonp.js

jsonp.js 1.0.0
(c) 2012 Alasdair Mercer
Freely distributable under the MIT license.
For all details and documentation:
http://neocotic.com/jsonp.js

 
(function (root) {

Private variables

 

  var

Initially the current time but incremented by each call to get in order to ensure unique identifiers.

 
    id            = (new Date()).getTime(),

Save the previous value of the JSONP variable.

 
    previousJSONP = root.JSONP,

Timeout IDs for removing callback functions where the timeout setting has been set.
IDs should be removed once either the callback is called or the request has timed out (as specified by the timeout setting).

 
    timers        = {};

Private functions

Simplest method for appending parameters to an existing query string.

 
  function paramify(data) {
    var query = '';
    for (var key in data) {
      if (data.hasOwnProperty(key)) {
        query += '&' + key + '=' + data[key];
      }
    }
    return query;
  }

JSONP setup

Build the publicly exposed API.

 
  var JSONP = {

Public Constants

Current version of JSONP.

 
    VERSION: '1.0.0',

Public Variables

Callback functions for activate JSONP requests.
Functions should removed once they have been called. If the timeout setting has been set and the function has not yet been called, that function will be removed.
This property must be public since the callback is called in global context.

 
    __callbacks__: {},

Name of the callback parameter included in the query string.

 
    callbackName: 'callback',

Timeout (in milliseconds) for the request. Requests will only be timed out if this is greater than zero.

 
    timeout: 0,

JSONP functions

Send the data provided to the URL and pass the callback function as a parameter to be called under the specified context. Only the url argument is required.

 
    get: function (url, data, callback, context) {

Ensure optional arguments are handled, using defaults where needed.

 
      if (typeof url      !== 'string'  ) return;
      if (typeof callback !== 'function') context = callback;
      if (typeof data     === 'function') callback = data;
      if (typeof data     !== 'object'  ) data = {};
      if (typeof callback !== 'function') callback = function () {};
      var
        head   = document.head || document.getElementsByTagName('head')[0] ||
                 document.documentElement,
        script = document.createElement('script');
      id++;
      JSONP.__callbacks__[id] = function A() {

Clear any timeout.

 
        clearTimeout(timers[id]);

Delete all references.

 
        delete timers[id];
        delete JSONP.__callbacks__[id];

Call the callback function with arguments.

 
        callback.apply(context, arguments);
      };

Build query string.

 
      url += (url.indexOf('?') === -1) ? '?' : '&';
      url += JSONP.callbackName + '=' +
             encodeURIComponent('JSONP.__callbacks__[' + id + ']');
      url += paramify(data);
      script.src = url;

Add script element to head, while preventing IE6 bug.

 
      head.insertBefore(script, head.firstChild);

Create timer if timeout setting is set.

 
      if (JSONP.timeout > 0) {
        timers[id] = setTimeout(function B() {

Delete all references.

 
          delete JSONP.__callbacks__[id];
          delete timers[id];

Remove the script element from head.

 
          if (head && script.parentNode) head.removeChild(script);

Dereference the script.

 
          script = null;
        }, JSONP.timeout);
      }
    },

Utility functions

Run jsonp.js in noConflict mode, returning the JSONP variable to its previous owner.
Returns a reference to JSONP.

 
    noConflict: function () {
      root.JSONP = previousJSONP;
      return this;
    }

  };

Support

Export JSONP for CommonJS.

 
  if (typeof define === 'function' && define.amd) {
    define('JSONP', function Z() {
      return JSONP;
    });
  } else {
    root.JSONP = JSONP;
  }

}(this));