Out of the box, Angular.js won’t work with IE8/IE9 because CORS is not fully implemented. Fortunately, XDomain offers a painless set-and-forget way to add full CORS support to IE8 and IE9. XDomain works by creating an iframe in the Angular app and loading a “proxy” from the API server. All XHRs are intercepted and rerouted through the iframe to the API server.

Configuring XDomain is really simple. Inside index.html, place a conditional comment for IE9 and below that loads the XDomain library and sets up the URLs of the slave proxies. xdomain.slaves expects a dictionary of host:path configuration data that specifies where it should load the slave proxy from for a given cross-domain host. Here’s a sample of what that might look like:

<!--[if lte IE 9]>

<script src="//cdn.rawgit.com/jpillora/xdomain/gh-pages/dist/0.6/xdomain.min.js"></script>

<script>
xdomain.slaves({
 "http://127.0.0.1:5000": "/static/proxy.html",
 "http://localhost:5000": "/static/proxy.html",
 "http://api.staging.com": "/static/proxy.html",
 "https://api.production.com": "/static/proxy.html"
});
</script>

<![endif]-->

Note that the XDomain slave configuration must happen before loading any other libraries to ensure that it’s hooks are installed properly. On the API server, you will need to host a proxy.html file that contains the configuration for the slaves. If your API server is using Flask, this is as simple as creating a static directory in the root of the Flask project and putting the proxy.html file there. Flask will serve files from this directory without any additional configuration. The slave configuration is very similar to the master’s configuration. xdomain.masters expects a dictionary of host:path data that specifies what paths the proxy should respond to for each given master:

<script src="//cdn.rawgit.com/jpillora/xdomain/gh-pages/dist/0.6/xdomain.min.js"></script>

<script>
xdomain.masters({
 "http://127.0.0.1:9000": "*",
 "http://localhost:9000": "*",
 "http://api.staging.com": "*",
 "https://api.production.com": "*"
});
</script>

Thats it! Legacy browser support in about 20 lines or less!