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.

http://bl.ocks.org/eyaler/10586116 Refer to this code, this is reading from a file and creating a graph. I also had the same problem, but later I figured out that the problem was in the json file I was using(an extra comma). If you are getting null here try printing the error you are getting, like this may be.

d3.json("filename.json", function(error, graph) {
  alert(error)
})

This is working in firefox, in chrome somehow its not printing the error.

Loading a local csv or json file with (d3)js is not safe to do. They prevent you from doing it. There are some solutions to get it working though. The following line basically does not work (csv or json) because it is a local import:

d3.csv("path_to_your_csv", function(data) {console.log(data) });

Solution 1: Disable the security in your browser

Different browsers have different security setting that you can disable. This solution can work and you can load your files. Disabling is however not advisable. It will make you vulnerable for all kind of threads. On the other hand, who is going to use your software if you tell them to manually disable the security?

Disable the security in Chrome:

--disable-web-security
--allow-file-access-from-files

Solution 2: Load your csv/json file from a website.

This may seem like a weird solution but it will work. It is an easy fix but can be unpractical though. See here for an example. Check out the page-source. This is the idea:

d3.csv("https://path_to_your_csv", function(data) {console.log(data) });

Solution 3: Start you own browser, with e.g. Python.

Such a browser does not include all kind of security checks. This may be a solution when you experiment with your code on your own machine. In many cases, this may not be the solution when you have users. This example will serve HTTP on port 8888 unless it is already taken:

python -m http.server 8888
python -m SimpleHTTPServer 8888 &

Open the (Chrome) browser address bar and type the underneath. This will open the index.html. In case you have a different name, type the path to that local HTML page.

localhost:8888

Solution 4: Use local-host and CORS

You may can use local-host and CORS but the approach is not user-friendly coz setting up this, may not be so straightforward.

Solution 5: Embed your data in the HTML file

I like this solution the most. Instead of loading your csv, you can write a script that embeds your data directly in the html. This will allow users use their favorite browser, and there are no security issues. This solution may not be so elegant because your html file can grow very hard depending on your data but it will work though. See here for an example. Check out the page-source.

Remove this line:

d3.csv("path_to_your_csv", function(data) { })

Replace with this:

var data = 
    [
        $DATA_COMES_HERE$
    ]