simple http request for json

http.js

// Do checks for minimum requirements
if (!XMLHttpRequest || !JSON) {
  throw Error('Browser does not support the minimum requirements of ' +
        'XMLHttpRequest, JSON' +
        '. Try adding modernizer to polyfill.');
}

function http(method, url, data, success) {
  var r = new XMLHttpRequest();
  r.open(method, url, true);
  r.onreadystatechange = function() {
    if (r.readyState == 4) {
      var resp = JSON.parse(r.responseText);
      if (resp && resp.error) {
        throw new Error(resp.error);
        return;
      }
      if (success) {
        success(resp);
      }
    }
  };
  r.setRequestHeader('Content-Type', 'application/json');
  if (data) {
    switch (toString.call(data)) {
      case '[object Object]':
        data = JSON.stringify(data);
        break;
      // case '[object String]':
      //   break;
      // case '[object FormData]':
      //   break;
    }
  }
  r.send(data);
}

http.GET = function(url, success) { http('GET', url, null, success); };
http.POST = function(url, data, success) { http('POST', url, data, success); };
http.DELETE = function(url, success) { http('DELETE', url, null, success); };