通过X射线/节点刮取黑客新闻

Question

如何通过x-ray / nodejs抓取黑客新闻（https://news.ycombinator.com/）？

我想从中得到这样的东西：

[
  {title1, comment1},
  {title2, comment2},
  ...
  {"‘Minimal’ cell raises stakes in race to harness synthetic life", 48}
  ...
  {title 30, comment 30}
]

有一张新闻表，但我不知道怎么刮它... 网站上的每个故事都由三列组成。它们没有父对象。所以结构看起来像这样

<tbody>
  <tr class="spacer"> //Markup 1
  <tr class="athing"> //Headline 1 ('.deadmark+ a' contains title)
  <tr class>          //Meta Information 1 (.age+ a contains comments)
  <tr class="spacer"> //Markup 2
  <tr class="athing"> //Headline 2 ('.deadmark+ a' contains title)
  <tr class>          //Meta Information 2 (.age+ a contains comments)
  ...
  <tr class="spacer"> //Markup 30
  <tr class="athing"> //Headline 30 ('.deadmark+ a' contains title)
  <tr class>          //Meta Information 30 (.age+ a contains comments)

到目前为止，我已尝试过：

x("https://news.ycombinator.com/", "tr", [{
  title: [".deadmark+ a"],
  comments: ".age+ a"
}])

和

x("https://news.ycombinator.com/", {
  title: [".deadmark+ a"],
  comments: [".age+ a"]
})

第二种方法返回30个名字和29个评论小丑...我认为没有任何可能将它们映射在一起，因为没有30个标题缺少评论的信息......

任何有用的帮助

Answer 1

由于存在no way to reference the current context in a CSS selector，因此使用X-ray包很容易抓取标记。这对于获取tr行之后的下一个tr.thing兄弟来获取评论非常有用。

我们仍然可以使用"next sibling" notation（+）到达下一行，但是，我们将获取完整的行文本，然后提取注释值与正则表达式。如果没有评论，请将值设置为0。

完整的工作代码：

var Xray = require('x-ray');
var x = Xray();

x("https://news.ycombinator.com/", {
    title: ["tr.athing .deadmark+ a"],
    comments: ["tr.athing + tr"]
})(function (err, obj) {
    // extracting comments and mapping into an array of objects
    var result = obj.comments.map(function (elm, index) {
        var match = elm.match(/(\d+) comments?/);
        return {
            title: obj.title[index],
            comments: match ? match[1]: "0"
        };
    });
    console.log(result);
});

目前正在打印：

[ { title: 'Follow the money: what Apple vs. the FBI is really about',
    comments: '85' },
  { title: 'Unable to open links in Safari, Mail or Messages on iOS 9.3',
    comments: '12' },
  { title: 'Gogs – Go Git Service', comments: '13' },
  { title: 'Ubuntu Tablet now available for pre-order',
    comments: '56' },
  ...
  { title: 'American Tech Giants Face Fight in Europe Over Encrypted Data',
    comments: '7' },
  { title: 'Moving Beyond the OOP Obsession', comments: '34' } ]