question

There following is a custom class method in my index.js:

function getCurrentTaskGuide() {
    if (this.attributes['currentTaskGuide'] == undefined) {
        this.attributes['currentTaskGuide'] = 1;
    }
    else if (!this.attributes['currentTaskGuide']) {
        this.attributes['currentTaskGuide'] = 1;
    }
    return this.attributes['currentTaskGuide'];
}

Within the same file, in my intent blocks, if I want to call the method, the following call works as desired:

var currentTaskGuide = getCurrentTaskGuide.call(this); 

However, the following always returns "undefined":

var currentTaskGuide = getCurrentTaskGuide();

I'm still learning Node.js but can someone explain why I have to use getCurrentTaskGuide.call(this) over getCurrentTaskGuide() ?