hxr-request.js

// load a file from a URL
function readTextFile(file, callback, errorback) {
    var rawFile = new XMLHttpRequest();
    // only change this if you know you want to force a particular mime type and are having trouble
    // rawFile.overrideMimeType("application/json");
    try {
        rawFile.open("GET", file, true);
    } catch (e) {
        console.error("Error opening file:", e);
    }
    rawFile.onreadystatechange = function() {
        // readyState 4 = done
        if (rawFile.readyState === 4 && rawFile.status == "200") {
            callback(rawFile.responseText);
        } else if (rawFile.readyState === 4 && rawFile.status == "404") {
            throw new Error("404 – can't load file", file);
        } else if (rawFile.readyState === 4 && rawFile.status == "401") {
            throw new Error("401 – can't load file", file);
        } else if (rawFile.readyState === 4) {
            throw new Error("Problem with "+ file);
        }
    };
    rawFile.send(null);
}

readTextFile(url, function(text){
	//  do the stuff!
    try {
        data = JSON.parse(text);
    } catch(e) {
        console.warn('Error parsing json:', e);
    }
}