This is the Datawrapper API reference, the place where you can find all endpoints and the documentation on how to fetch data, what query parameters can be used or how the JSON to create a chart should look.
Note that the Datawrapper API is designed to be used in server-side scripts (or from a script on your computer). For security reasons, it is not possible to call the Datawrapper API from the browser. In case you need to do that, you can build a proxy around the endpoints that you need to call from the browser.