JavaScript code example of this in anonymous, callback, arrow function, es6, es5

about_this.js

{
class Message {
    doCallback(cb){
        cb("!!");
    }
    doAnother(){
        console.log("??", this); // Message
    }
    doSomething() {
        this.doCallback(function(message){
            this.doAnother(); // undefined
        })
    }

}
(new Message).doSomething();
}


{
class Message {
    doCallback(cb){
        cb("!!");
    }
    doAnother(){
        console.log("??", this); // Message
    }
    doSomething() {
        this.doCallback((message) => {
            this.doAnother(); // this: undefined, but arrow function doesn't create its own this context.
        })
    }

}
(new Message).doSomething();
}


(function(){

function Message(){
}
Message.prototype = {
    doCallback: function(cb){
        cb("!!");
    },
    doAnother: function(){
        console.log("??", this); // Message
    },
    doSomething: function() {
        this.doCallback(function(message){
            this.doAnother(); // this: Window, so maybe doAnother is undefined
        })
    }
}
var message = new Message()
message.doSomething();
   
})();