The loading of a .json file from a hard disk is an asynchronous operation, and thus it needs to specify a callback function to execute after the file is loaded.

function readTextFile(file, callback) {
    var rawFile = new XMLHttpRequest();
    rawFile.overrideMimeType("application/json");
    rawFile.open("GET", file, true);
    rawFile.onreadystatechange = function() {
        if (rawFile.readyState === 4 && rawFile.status == "200") {
            callback(rawFile.responseText);
        }
    }
    rawFile.send(null);
}

//usage:
readTextFile("/Users/Documents/workspace/test.json", function(text){
    var data = JSON.parse(text);
    console.log(data);
});

This function also works for loading a .html or .txt files, by overriding the mime type parameter to "text/html", "text/plain", etc.

This solution uses an Asynchronous call. It will likely work better than a synchronous solution.

var request = new XMLHttpRequest();
request.open("GET", "../../data/file.json", false);
request.send(null);
request.onreadystatechange = function() {
  if ( request.readyState === 4 && request.status === 200 ) {
    var my_JSON_object = JSON.parse(request.responseText);
    console.log(my_JSON_object);
  }
}