[](https://travis-ci.org/PolymerElements/iron-ajax) _[Demo and API docs](https://elements.polymer-project.org/elements/iron-ajax)_ ## Changes in 2.0 * Promise polyfill is now a dev dependency and no longer shipped with `iron-ajax`. `iron-ajax` uses the `Promise` API, which is not yet supported in all browsers. The 1.x version of `iron-ajax` automatically loaded the promise polyfill. This forced the application to include the polyfill, whether or not it was needed. When using `iron-ajax` 2.x with Polymer 1.x, you must provide your own Promise polyfill, if needed. For example, you could use the promise polyfill by installing it in your project: bower install --save PolymerLabs/promise-polyfill#1 - 2 Then your app should include the promise polyfill before loading `iron-ajax`: You can use a different promise polyfill if you need a more fully-featured implementation of Promise. For Polymer 2.x, you **do not need to provide your own Promise polyfill if you are using the web components polyfills.** Because the web components v1 APIs depend on `Promise`, a promise polyfill is loaded when needed by the v1 polyfills (`web-components-lite.js` or `webcomponents-loader.js`). * New optional error information. The `generateRequest` method returns an `iron-request` element representing the request, and the request element provides a `completes` property, which is a promise that completes when the request either succeeds or fails. This version includes a new flag, `rejectWithRequest`, that modifies the error handling of the `completes` promise. By default, when the promise is rejected (because the request failed), the rejection callback only receives an `Error` object describing the failure. With `rejectWithRequest` set to true, the callback receives an object with two keys, `error`, the error message, and `request`, the original request that the error is related to: let request = ironAjaxElement.generateRequest(); request.completes.then(function(req) { // succesful request, argument is iron-request element ... }, function(rejected) { // failed request, argument is an object let req = rejected.request; let error = rejected.error; ... } ) Because this change could break existing code, `rejectWithRequest` is false by default, however, in the next major release, this option will be removed and the new behavior made the default. ## <iron-ajax> The `iron-ajax` element exposes network request functionality. ```html ``` With `auto` set to `true`, the element performs a request whenever its `url`, `params` or `body` properties are changed. Automatically generated requests will be debounced in the case that multiple attributes are changed sequentially. Note: The `params` attribute must be double quoted JSON. You can trigger a request explicitly by calling `generateRequest` on the element. ## <iron-request> iron-request can be used to perform XMLHttpRequests. ```html ... this.$.xhr.send({url: url, body: params}); ```