Why am I getting an infinite for loop using javascript?

Question

I am trying to create a bookshelf with various books. However, when I attempt to make a new bookshelf for every 4 books, I get an error. Possibly an infinite for loop? What is going wrong? (Khan Academy Program)

An array of books.

var book = [
    {
        title: "The Giver",
        stars: 4,
        author: "Lois Lowry",//2.Author property to each book                                  added #1
        color: color(0, 120, 42),//3. Property that stores                                          color
        recommended: true
    },
    {
        title: "NWT of the Holy Scriptures",
        stars: 5,
        author: "Jehovah",//2.Author property... #2
        color: color(204, 204, 204),//3. Property that stores                                          color
        recommended: true
    },
    {
        title: "The Cay",
        stars: 4,
        author: "Theodore Taylor",//2.Author property... #3
        color: color(80, 84, 209),//3. Property that stores                                          color
        recommended: true
    },
    {
        title: "The Golden Compass",
        stars: 5,
        author: "Philip Pullman",//2.Author property... #4
        color: color(97, 55, 186),//3. Property that stores                                          color
        recommended: true
    },
];

Draw bookshelves and books

for(var x = 0; x < book.length; x++){
    //Draw books
    fill(book[x].color);
    rect(5 + 100 * x, 20, 90, 100);
    fill(0, 0, 0);
    text(book[x].title, 15 + 100 * x, 29, 70, 100);
    text(book[x].author,35 + 100 * x, 76, 70, 100);

    //Draw leaf for recommended books
    if(book[x].recommended === true){
        var leaf = getImage("avatars/leaf-red");
        image(leaf, 10 + 100 * x, 85,25,25);
    }
    //Draw stars for star rating
    for (var i = 0; i < book[x].stars; i++) {
        image(getImage("cute/Star"), 17 + i * 15 + 100 * x, 96         , 15, 25);
    }
    //Draw bookshelf for every 4 books
    for(var y = book.length;y >= 0;y - 4){
        // draw shelf
        fill(87, 10, 0);
        rect(0, 120 + 100 * y, width, 10);
    }/// <------ infinite loop?
}

You should assign the reduced value back to y, like this y -= 4 — thefourtheye
– thefourtheye, Commented Apr 4, 2015 at 6:37
Please post in answer section so I can accept your answer :) Thank you! — Sally A.
– Sally A., Commented Apr 4, 2015 at 6:43

Dai · Accepted Answer · 2015-04-04 07:06:35Z

1

for(var y = book.length;y >= 0;y - 4){

...is not actually mutating the value of y. Change it to:

for( var y = book.length; y >= 0; y -= 4 ) {

edited Apr 4, 2015 at 7:06

answered Apr 4, 2015 at 6:39

Dai

157k31 gold badges314 silver badges436 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why am I getting an infinite for loop using javascript?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related