Question about best practice with JS objects and internal method calls

example.js

messageOfTheDay = function (appName) {
	this.appName = appName;
	if (this.lastMessageText === undefined) {
		this.lastMessageText = "";
		}
	this.sayHello = function () {
		console.log ("hello");
		}
	this.checkForUpdate = function () {
		var urlTextFile = "http://1999.io/testing/motd/" + this.appName + ".txt";
		var motd = this;
		readHttpFile (urlTextFile, function (s) {
			if (s !== undefined) {
				if (s !== this.lastMessageText) {
					this.lastMessageText = s;
					console.log ("messageOfTheDay.checkForUpdate: s == " + s);
					motd.sayHello ();
					}
				}
			});
		}
	};

Allen, you're absolutely right about this.lastMessageText.

It clearly refers to an object that belongs to the callback to readHttpFile.

It's a mistake -- and I'll need to think about how it works and fix it.

BTW, re ES6, I'm not using any ES6 features yet.

I found a subset of JS that works for me, and then proceeded to develop the functionality I wanted. There's a lot of that so it hasn't left much time for exploring new language functionality. That's the way my brain works. It's why I don't like people figuring out how to fix "callback hell" -- I've made my peace with it, and would prefer not to learn another way to do something I already know how to do.

At age 61, I'm kind of "set in my ways" in this regard. ;-)