scrapy-splash 如何处理无限滚动？

Question

我想对在网页中向下滚动生成的内容进行逆向工程。问题出在网址https://www.crowdfunder.com/user/following_page/80159?user_id=80159&limit=0&per_page=20&screwrand=933 中。 screwrand 似乎没有遵循任何模式，因此反转 url 不起作用。我正在考虑使用 Splash 进行自动渲染。如何使用 Splash 像浏览器一样滚动？非常感谢！ 以下是两个请求的代码：

request1 = scrapy_splash.SplashRequest(
    'https://www.crowdfunder.com/user/following/{}'.format(user_id),
     self.parse_follow_relationship,
     args={'wait':2},
     meta={'user_id':user_id, 'action':'following'},
     endpoint='http://192.168.99.100:8050/render.html')

yield request1

request2 = scrapy_splash.SplashRequest(
    'https://www.crowdfunder.com/user/following_user/80159?user_id=80159&limit=0&per_page=20&screwrand=76',
    self.parse_tmp,
    meta={'user_id':user_id, 'action':'following'},
    endpoint='http://192.168.99.100:8050/render.html')

yield request2

ajax request shown in browser console

Answer 1

要滚动页面，您可以编写自定义渲染脚本（请参阅http://splash.readthedocs.io/en/stable/scripting-tutorial.html），如下所示：

function main(splash)
    local num_scrolls = 10
    local scroll_delay = 1.0

    local scroll_to = splash:jsfunc("window.scrollTo")
    local get_body_height = splash:jsfunc(
        "function() {return document.body.scrollHeight;}"
    )
    assert(splash:go(splash.args.url))
    splash:wait(splash.args.wait)

    for _ = 1, num_scrolls do
        scroll_to(0, get_body_height())
        splash:wait(scroll_delay)
    end        
    return splash:html()
end

要渲染此脚本，请使用“执行”端点而不是 render.html 端点：

script = """<Lua script> """
scrapy_splash.SplashRequest(url, self.parse,
                            endpoint='execute', 
                            args={'wait':2, 'lua_source': script}, ...)

Answer 2

感谢 Mikhail，我尝试了你的滚动脚本，它成功了，但我也注意到你的脚本滚动一次太多，一些 js 没有时间渲染并被跳过，所以我做了一些小改动如下：

function main(splash)
        local num_scrolls = 10
        local scroll_delay = 1

        local scroll_to = splash:jsfunc("window.scrollTo")
        local get_body_height = splash:jsfunc(
            "function() {return document.body.scrollHeight;}"
        )
        assert(splash:go(splash.args.url))
        splash:wait(splash.args.wait)

        for _ = 1, num_scrolls do
            local height = get_body_height()
            for i = 1, 10 do
                scroll_to(0, height * i/10)
                splash:wait(scroll_delay/10)
            end
        end        
        return splash:html()
end

Answer 3

我不认为硬编码设置滚动次数对于无限滚动页面是一个好主意，所以我将上述代码修改为：

function main(splash, args)
    
    current_scroll = 0  
  
    scroll_to = splash:jsfunc("window.scrollTo")
    get_body_height = splash:jsfunc(
        "function() {return document.body.scrollHeight;}"
    )
    assert(splash:go(splash.args.url))
    splash:wait(3)
  
    height = get_body_height()

    while current_scroll < height do
        scroll_to(0, get_body_height())
        splash:wait(5)
            current_scroll = height
            height = get_body_height()
    end 
    splash:set_viewport_full()
    return splash:html()
end