Often when developing complex client side apps, a simple python -m SimpleHTTPServer can host the html. For a node backend though, a second server has to be run to host the REST api, which must be on a different domain. For example the python server is on port 8000, whereas the REST server is run on port 3000.

This will usually throw an error containing the script

Origin https://localhost:8000 is not allowed by Access-Control-Allow-Origin

This is a security measure input by web browsers to prevent cross domain scripting attacks, and is a good idea, but during development this can be a problem.

One option is to use a fully featured web server e.g. express but for rich client side applications this is generally overkill, a simpler library such as restify is ideal.

A nice option as supplied by this SO answer is to add middleware to allow certain domains access to the REST server.

For development this is a handy workaround, but for production obviously DO NOT USE!

For restify this can be inserted before your normal CRUD routes as middleware using server.use(...).