quick and dirty python->javascript version of repack.py

repack.js

class Rect {
    constructor(left, top, right, bottom) {
        this.left = left;
        this.top = top;
        this.right = right;
        this.bottom = bottom;
    }
    width() { return this.right - this.left; }
    height() { return this.bottom - this.top; }
}

class Page {
    constructor(width, height) {
        this.width = width;
        this.height = height;
        this.free_rects = [new Rect(0, 0, width, height)];
        this.occupied_rects = [];
    }

    static *external_clipped_rects(a, b) {
        let top = a.top, bottom = a.bottom;
        if (a.top < b.top) {
            top = b.top;
            yield new Rect(a.left, a.top, a.right, b.top);
        }
        if (a.bottom > b.bottom) {
            bottom = b.bottom;
            yield new Rect(a.left, b.bottom, a.right, a.bottom);
        }
        if (a.left < b.left) {
            yield new Rect(a.left, top, b.left, bottom);
        }
        if (a.right > b.right) {
            yield new Rect(b.right, top, a.right, b.bottom);
        }
    }

    insert(width, height) {
        for (let i = 0; i < this.free_rects.length; ++i) {
            const free_rect = this.free_rects[i];
            if (free_rect.width() < width || free_rect.height() < height) continue;
            const rect = new Rect(free_rect.left, free_rect.top, free_rect.left + width, free_rect.top + height);
            this.occupied_rects.push(rect);
            this.free_rects.splice(i, 1); // Remove free_rect at index i
            let free_count = this.free_rects.length;
            for (const clipped_rect of Page.external_clipped_rects(free_rect, rect)) {
                this.free_rects.push(clipped_rect);
            }
            if (free_count !== this.free_rects.length) {
                this.free_rects.sort((x, y) => (x.height() - y.height()));
            }
            return rect;
        }
        return null;
    }

    calculate_efficency() {
        const total_area = this.width * this.height;
        let used_area = 0;
        for (const rect of this.occupied_rects) {
            used_area += rect.width() * rect.height();
        }
        return used_area / total_area;
    }
}

class Packer {
    constructor(width, height) {
        this.pages = [new Page(width, height)];
        this.page_width = width;
        this.page_height = height;
    }

    insert(width, height) {
        for (const page of this.pages) {
            const rect = page.insert(width, height);
            if (rect) return { page: page, rect: rect };
        }
        const new_page = new Page(this.page_width, this.page_height);
        this.pages.push(new_page);
        const rect = new_page.insert(width, height);
        return { page: new_page, rect: rect };
    }
}