Node.js Puppeteer 等待所有图像加载然后截图

我用Puppeteer来try 在所有图片加载后拍摄一个网站的截图，但无法让它工作.

以下是我到目前为止获得的代码，我使用https://www.digg.com作为示例网站:

const puppeteer = require('puppeteer');

(async () => {
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto('https://www.digg.com/');

    await page.setViewport({width: 1640, height: 800});

    await page.evaluate(() => {
        return Promise.resolve(window.scrollTo(0,document.body.scrollHeight));
    });

    await page.waitFor(1000);

    await page.evaluate(() => {
        var images = document.querySelectorAll('img');

        function preLoad() {

            var promises = [];

            function loadImage(img) {
                return new Promise(function(resolve,reject) {
                    if (img.complete) {
                        resolve(img)
                    }
                    img.onload = function() {
                        resolve(img);
                    };
                    img.onerror = function(e) {
                        resolve(img);
                    };
                })
            }

            for (var i = 0; i < images.length; i++)
            {
                promises.push(loadImage(images[i]));
            }

            return Promise.all(promises);
        }

        return preLoad();
    });

    await page.screenshot({path: 'digg.png', fullPage: true});

    browser.close();
})();