Javascript objects calling function from itself

Question

I've been reading Game Design with HTML5 and JavaScript and it introduced me to objects. So after reading the book and working on the projects I decided to take this new found knowledge and integrate objects in my own projects. So here's my question can or should objects call their own functions? For example:

var someObject = {
    start: function() {
        check();
    },
    check: function() {
        console.log("Check!");
    }
};

someObject.start();

The book did show an example with a timer that does this:

var timer = {
    start: function() {
        var self = this;
        window.setInterval(function(){self.tick();}, 1000);
    },
    tick: function() {
        console.log('tick!');
    }
};

In the example with timer object it makes a reference to self in order to call the internal function, so does this mean I should use self to call internal functions or is this the proper way to do this with objects? Or best practices? Thanks in advance.

var someObject = {
    start: function() {
        var self = this;
        self.check();
    },
    check: function() {
        console.log("Check!");
    }
};

someObject.start();

Answer 1

JavaScript names are lexically scoped, so whenever a name (variable) is encountered in a script, the JavaScript runtime must search up the scopes from where the function was defined.

At the point of definition, this function:

start: function() {
    check();
}

doesn't have access to any check function in its outer scope. Declaring self and binding it to this is a technique used to deal with the (somewhat interesting) intricacies of referring to the current object in JavaScript (because the example code uses window.setInterval).

To reference a function within the current object, it is enough to use this.

var someObject = {
    start: function() {
        this.check();
    },
    check: function() {
        console.log("Check!");
    }
};