Javascript - 使用日期函数运行模拟的原型函数

Question

I am trying to add two functions to my program. One of them will change the available property of the prototype from true to false and set the checkout date. The checkout date needs to be set to the current date minus some random number of days (days should be randomized).

My try:

    Book.prototype.checkOut = function() {
    this.Available = false;
    var temp = new Date(1000000000);
    var date = new Date() - temp;
    var res = new Date(date);
    this.checkoutDate = res;
};

The second one checks the current date and the checked out date and if it's greater than 14 days it returns true.

My try:

    Book.prototype.isOverdue = function() {
    var singleDay = 1000 * 60 * 60 * 24;
    var todayDate = new Date().getTime();
    var difference = todayDate - this.checkoutDate.getTime();
    if (Math.round(difference / singleDay) >= 14) {
        return true;
    }
    return false;
};

All my code:

 var Book = function(title, Available, publicationDate, checkoutDate, callNumber, Authors) { this.title = title; this.Available = Available; this.publicationDate = publicationDate; this.checkoutDate = checkoutDate; this.callNumber = callNumber; this.Authors = Authors; }; var Author = function(firstName, lastName) { this.firstName = firstName; this.lastName = lastName; }; var Patron = function(firstName, lastName, libCardNum, booksOut, fine) { this.firstName = firstName; this.lastName = lastName; this.libCardNum = libCardNum; this.booksOut = booksOut; this.fine = fine; }; Book.prototype.checkOut = function() { this.Available = false; var temp = new Date(1000000000); var date = new Date() - temp; var res = new Date(date); this.checkoutDate = res; }; Book.prototype.checkIn = function() { this.Available = true; }; Book.prototype.isOverdue = function() { var singleDay = 1000 * 60 * 60 * 24; var todayDate = new Date().getTime(); var difference = todayDate - this.checkoutDate.getTime(); if (Math.round(difference / singleDay) >= 14) { return true; } return false; }; Patron.prototype.read = function(book) { this.booksOut.add(book); } Patron.prototype.return = function(book) { this.booksOut.remove(this.booksOut.length); } var authors = []; authors[0] = new Author("Auth", "One"); authors[1] = new Author("AutL", "Two"); var catalog = []; catalog[0] = new Book('Bk1', true, new Date(2001, 1, 21), new Date(), 123456, authors); catalog[1] = new Book('Bk2', true, new Date(2002, 2, 22), new Date(), 987656, authors); catalog[2] = new Book('Bk3', true, new Date(2003, 3, 23), new Date(), 092673, authors); catalog[3] = new Book('Bk4', true, new Date(2004, 4, 24), new Date(), 658342, authors); catalog[4] = new Book('Bk5', true, new Date(2005, 5, 25), new Date(), 345678, authors); var patrons = []; patrons[0] = new Patron('Pat1', 'Wat', 1, catalog, 0.00); patrons[1] = new Patron('Pat2', 'Wot', 1, catalog, 0.00); patrons[2] = new Patron('Pat3', 'Wit', 1, catalog, 0.00); patrons[3] = new Patron('Pat4', 'Wet', 1, catalog, 0.00); patrons[4] = new Patron('Pat5', 'Wut', 1, catalog, 0.00); //while loop or for loop for 90 days //For loop over catalog //forloop over patrons //Check if available , if so check book out //If not available check book back in //check checking back in check to see if book is overdue and if so add a fine //When down loop over patrons to see their fees for (var i = 0; i < 90; i++) { for (var j = 0; j < catalog.length; j++) { for (var k = 0; k < patrons.length; k++) { var fine = patrons[k].fine; if (catalog[k].Available) { catalog[k].checkOut; } else { catalog[k].checkIn; patrons[k].read; } if (catalog[k].isOverdue) { fine = fine + 5.00; } patrons[k].fine = fine; } } } for (i = 0; i < patrons.length; i++) { console.log(patrons[i].firstName + " has checked out the following books:"); for (j = 0; j < patrons[i].booksOut.length; j++) { console.log(patrons[i].booksOut[j].title); } console.log(patrons[i].firstName + " has fine amount: $" + patrons[i].fine); } 

When I run the program, everything runs but the patrons end up getting huge fines, and as this is supposed to be a randomized simulation, I can't seem to figure out what I should do differently to fix that problem.

Answer 1

You say:

The checkout date needs to be set to the current date minus some random number of days (days should be randomized).

yet there is no radomisation in:

Book.prototype.checkOut = function() {
  this.Available = false;
  var temp = new Date(1000000000);
  var date = new Date() - temp;
  var res = new Date(date);
  this.checkoutDate = res; 
};

The expression new Date(1000000000) returns a new date for 1970-01-12T13:46:40.000Z, so

new Date() - temp;

returns a large number, like 1491816607452, which is about 1726 days. It sets the same expiry date for all patrons for all books, so they all end up with the same fine.

If you want to have patrons checkout books for random periods of say 10 to 20 days, then:

 // Return a random integer between start and end inclusive // Does not check if start or end are integers function randInRange(start, end) { return Math.floor(Math.random() * (end - start + 1)) + start; } // checkOut method as function for demo var checkOut = function() { // Set randDays to random days from 10 to 20 var randDays = randInRange(10,20); // return date minus randDays var date = new Date(); date.setDate(date.getDate() - randDays); return date; }; // Some tests, 10 dates randomly 10 to 20 days ago for (var i=10; i; i--) { console.log(checkOut().toString()); } 

The checkOut method is a plain function that you can modify to suit your Book constructor. But rather than radomising your test data, it should be set to specific values so you know exactly what the results should be. Also, you should test known problematic cases to ensure they are handled correctly.

I haven't looked at the rest of your code in any detail.