Is it possible to write data to a locally json file with nothing but angular?

No.

Angular runs client side.

If you want to write data to the server (even one on the same computer as the browser) then you need server side code to do it.

You can't access the local filesystem (directly) from Javascript. This is enforced for security reasons (and makes sense when you think about it!).

Local file access with javascript

Is it possible to write data to a locally json file with nothing but angular?

No. Even if you're running the page from the local file system (e.g., file://myfile.html) or from a local webserver (e.g., http://localhost/myfile.html or http://host-on-my-intranet/myfile.html), you still have no means of directly writing to a file from browser-hosted JavaScript code.

Two choices:

1. Send it to something (e.g., a server) that can write it out, or

2. Provide it as a data: URI (if feasible in your case) that the user can right-click and choose "save as..."

   Here's how you create a data: URI for some JSON text:

   var uri = "data:application/json;charset=UTF-8," + encodeURIComponent(theJSON);
   

Full Example of #2:

var theData = {
  foo: "bar"
};
var theJSON = JSON.stringify(theData);
var uri = "data:application/json;charset=UTF-8," + encodeURIComponent(theJSON);

var a = document.createElement('a');
a.href = uri;
a.innerHTML = "Right-click and choose 'save as...'";
document.body.appendChild(a);