index.js

/**
 * Module dependencies.
 */

var encode = require('base64-encode');
var cors = require('has-cors');
var jsonp = require('jsonp');
var JSON = require('json');

/**
 * Expose `send`
 */

exports = module.exports = cors
  ? json
  : base64;

/**
 * Expose `callback`
 */

exports.callback = 'callback';

/**
 * Expose `prefix`
 */

exports.prefix = 'data';

/**
 * Expose `json`.
 */

exports.json = json;

/**
 * Expose `base64`.
 */

exports.base64 = base64;

/**
 * Expose `type`
 */

exports.type = cors
  ? 'xhr'
  : 'jsonp';

/**
 * Send the given `obj` to `url` with `fn(err, req)`.
 *
 * @param {String} url
 * @param {Object} obj
 * @param {Object} headers
 * @param {Object} props
 * @param {Function} fn
 * @api private
 */

function json(url, obj, headers, props, fn){
  if (3 == arguments.length) fn = headers, headers = {}, props = {};
  if (4 == arguments.length) fn = props, props = {};

  var req = new XMLHttpRequest;
  req.onerror = fn;
  req.onreadystatechange = done;
  req.open('POST', url, true);
  for (var p in props) req[p] = props[p];
  for (var k in headers) req.setRequestHeader(k, headers[k]);
  req.send(JSON.stringify(obj));

  function done(){
    if (4 == req.readyState) return fn(null, req);
  }
}

/**
 * Send the given `obj` to `url` with `fn(err, req)`.
 *
 * @param {String} url
 * @param {Object} obj
 * @param {Function} fn
 * @api private
 */

function base64(url, obj, _, fn){
  if (3 == arguments.length) fn = _;
  var prefix = exports.prefix;
  obj = encode(JSON.stringify(obj));
  obj = encodeURIComponent(obj);
  url += '?' + prefix + '=' + obj;
  jsonp(url, { param: exports.callback }, function(err, obj){
    if (err) return fn(err);
    fn(null, {
      url: url,
      body: obj
    });
  });
}