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JavaScript Practice Object Interaction Checking Out and Returning a Book Solution: Charging Fines to Patrons

Posted by Michael Cook
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Michael Cook
Full Stack JavaScript Techdegree Graduate 28,975 Points

My chargeFines method

My chargeFines method is this: 

chargeFines = () => {
        this.patrons.filter(patron => patron.out)
            .forEach(patron => {
                const today = new Date();
                if (today > patron.currentBook.dueDate) {
                    const day = today.getDate();
                    const due = patron.currentBook.dueDate.getDate();
                    const daysLate = day - due;
                    patron.balance = daysLate * this.dailyFine;
                }
        });
    }

I think it is actually a more elegant solution than Ashley's, but could someone with more experience critique it and tell me if I am on the right track? Thanks!

1 Answer

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

Did you test this? I'm wondering because arrow functions do not define a "this" like conventional functions do.

Michael Cook
.a{fill-rule:evenodd;}techdegree seal-36
Michael Cook
Full Stack JavaScript Techdegree Graduate 28,975 Points

After I posted this I did end up testing it and it does produce the desired behaviour. However I am now wondering if there is a more efficient way of writing the function. Steven do you think you could point me to a resource you know of explaining this in the context of arrow functions?

Steven Parker
Steven Parker
231,236 Points
Steven Parker
Steven Parker
231,236 Points

MDN is my "go to" reference for all things front-end. Here's the page on Arrow Functions.
Look for the highlighted section titled "No separate this".

But also note that MDN advises "Arrow function expressions are ill suited as methods..."

Michael Cook
.a{fill-rule:evenodd;}techdegree seal-36
Michael Cook
Full Stack JavaScript Techdegree Graduate 28,975 Points

Thank you very much.