Importing local json file using d3.json does not work

If you're running in a browser, you cannot load local files.

But it's fairly easy to run a dev server, on the commandline, simply cd into the directory with your files, then:

python -m SimpleHTTPServer

(or python -m http.server using python 3)

Now in your browser, go to localhost:3000 (or :8000 or whatever is shown on the commandline).

The following used to work in older versions of d3:

var json = {"my": "json"};d3.json(json, function(json) {    root = json;    root.x0 = h / 2;    root.y0 = 0;});

In version d3.v5, you should do it as

d3.json("file.json").then(function(data){ console.log(data)});

Similarly, with csv and other file formats.

You can find more details at https://github.com/d3/d3/blob/master/CHANGES.md

Adding to the previous answers it's simpler to use an HTTP server provided by most Linux/ Mac machines (just by having python installed).

Run the following command in the root of your project

python -m SimpleHTTPServer

Then instead of accessing file://.....index.html open your browser on http://localhost:8080 or the port provided by running the server. This way will make the browser fetch all the files in your project without being blocked.