TypeError：尝试创建对象数组时分配给常量变量

Question

我一直在研究一个抓取工具，一切都很好，直到我尝试将抓取的数据对象推送到一个数组中。

现在我有这个：

exports.parseData = (getLink, getDescription, getPrice, getPicture) => {
  const apartments = [];
  apartments = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };
  console.log(apartments);
};

但它会抛出错误：TypeError: Assignment to constant variable。

现在我认为这是因为数据是如何发送到解析器的。 以下是我使用此代码时数据的外观：

exports.parseData = (getLink, getDescription, getPrice, getPicture) => {
  console.log(getLink);
  console.log(getDescription);
  console.log(getPrice);
  console.log(getPicture);
  console.log('-----------------');
};

https://www.sant.ba/nekretnine/nekretnina-3467-dvosoban-stan-sa-liftom-u-samom-centru-grada-63-m2
 dvosoban stan sa liftom u samom centru grada , 63 m2 
199000.00
https://www.sant.ba/thumb.php?file=photos/3467/3467_1_1563271355.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3689-troiposoban-stan-u-naselju-sunca
 Troiposoban stan u naselju Sunca
360000.00
https://www.sant.ba/thumb.php?file=photos/3689/3689_1_1612344465.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3677-trosoban-renoviran-stan-u-naselju-dolac-malta-73-m2
 trosoban, renoviran stan u naselju Dolac malta, 73 m2
150000.00
https://www.sant.ba/thumb.php?file=photos/3677/3677_1_1608550332.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3537-cetverosoban-stan-u-novogradnji-sa-prelijepim-pogledom-na-grad-118-38-m2
 Četverosoban stan u novogradnji sa prelijepim pogledom na grad, 118,38 m2 
538090.37
https://www.sant.ba/thumb.php?file=photos/3537/3537_1_1573217155.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3536-trosoban-stan-u-novogradnji-sa-prelijepim-pogledom-na-grad-105-34-m2
 Trosoban stan u novogradnji sa prelijepim pogledom na grad, 105,34 m2
478817.70
https://www.sant.ba/thumb.php?file=photos/3536/3536_2_1573216638.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3535-luksuzni-cetverosoban-stan-na-cobaniji-117-43m2
 Luksuzni četverosoban stan na Čobaniji,117,43m2
533772.19
https://www.sant.ba/thumb.php?file=photos/3535/3535_13_1573215220.jpg&maxw=273&maxh=205
-----------------
https://www.sant.ba/nekretnine/nekretnina-3534-trosoban-stan-u-novogradnji-90-m2
 trosoban stan u novogradnji, 90 m2
376923.46
https://www.sant.ba/thumb.php?file=photos/3534/3534_8_1573214216.jpg&maxw=273&maxh=205
-----------------
etc....

现在我想要的输出是：拥有一个对象数组，其中对象填充有数据，如上例所示。因此，为每个getLink, getDescription, getPrice, getPicture 创建新对象并将其推送到数组中（就像我在第一个代码块中使用它一样）。

我想得到的输出是：

[
   {
   
      link: https://www.sant.ba/nekretnine/nekretnina-3467-dvosoban-stan-sa-liftom-u-samom-centru-grada-63-m2
      descr: dvosoban stan sa liftom u samom centru grada , 63 m2 
      price: 199000.00
       picture: https://www.sant.ba/thumb.php?file=photos/3467/3467_1_1563271355.jpg&maxw=273&maxh=205
   },
   {
     link:https://www.sant.ba/nekretnine/nekretnina-3689-troiposoban-stan-u-naselju-sunca
     descr: Troiposoban stan u naselju Sunca
     price: 360000.00
     picture: https://www.sant.ba/thumb.php?file=photos/3689/3689_1_1612344465.jpg&maxw=273&maxh=205
   },
   etc...
]

这样的事情容易实现吗？ 谢谢！

这里是这些变量的发送位置：

const cheerio = require('cheerio');
const axios = require('axios');
const parsing = require('./parseData');

exports.olxScraper = () => {
  const url =
    'https://www.olx.ba/pretraga?vrsta=samoprodaja&kategorija=23&sort_order=desc&kanton=9&sacijenom=sacijenom&stranica=1';

  const getRawData = async () => {
    try {
      await axios.get(url).then((res) => {
        const $ = cheerio.load(res.data);
        $('div[id="rezultatipretrage"] > div')
          .not('div[class="listitem artikal obicniArtikal  i index"]')
          .not('div[class="obicniArtikal"]')
          .each((index, element) => {
            $('span[class="prekrizenacijena"]').remove();
            const getLink = $(element)
              .find('div[class="naslov"] > a')
              .attr('href');
            const getDescription = $(element)
              .find('div[class="naslov"] > a > p')
              .text();
            const getPrice = $(element)
              .find('div[class="datum"] > span')
              .text()
              .replace(/\.| ?KM$/g, '')
              .replace(' ', '');
            const getPicture = $(element)
              .find('div[class="slika"] > img')
              .attr('src');

            parsing.parseData(getLink, getDescription, getPrice, getPicture);
          });
      });
    } catch (error) {
      console.log(error);
    }
  };
  getRawData();
};

exports.santScraper = () => {
  const url = `https://www.sant.ba/pretraga/prodaja-1/tip-2/cijena_min-20000/stranica-1`;

  const getRawData = async () => {
    try {
      await axios.get(url).then((response) => {
        const $ = cheerio.load(response.data);

        $('div[class="col-xxs-12 col-xss-6 col-xs-6 col-sm-6 col-lg-4"]').each(
          (index, element) => {
            const getLink = $(element).find('a[class="re-image"]').attr('href');
            const getDescription = $(element).find('a[class="title"]').text();
            const getPrice = $(element)
              .find('div[class="prices"] > h3[class="price"]')
              .text()
              .replace(/\.| ?KM$/g, '')
              .replace(',', '.');
            const getPicture = $(element).find('img').attr('data-original');
            /*const getSquaremeters = $(element)
        .find('span[class="infoCount"]')
        .first()
        .text()
        .replace(',', '.')
        .split('m')[0];

      const pricepersquaremeter =
        parseFloat(getPrice) / parseFloat(getSquaremeters);
      articles[index] = {
        id: getLink.substring(42, 46),
        link: getLink,
        descr: getDescription,
        price: Math.round(getPrice),
        pictures: getPicture,
        sqm: Math.round(getSquaremeters),
        ppm2: Math.round(pricepersquaremeter),
      };*/
            parsing.parseData(getLink, getDescription, getPrice, getPicture);
          }
        );
      });
    } catch (error) {
      console.log(console.log(error));
    }
  };
  getRawData();
};

this.olxScraper();
this.santScraper();

Answer 1

当你声明一个常量时，引用不能改变。在您的代码中它显示const apartments = []，因此您将 const 声明为一个数组，然后尝试将 const 声明为一个对象。

试试

apartments.push({
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  });

Answer 2

您的代码不止一个问题：

1. 您不能重新分配 const 变量。

    const apartments = [];
    apartments = { ... };  //this is not allowed, becasue apartments is const.
   

2. 您将apartments 定义为一个数组，然后尝试将一个对象分配给同一个变量。这在 javascript 中是允许的，但可能不是你想要的......

编辑

至于您的评论：如果您希望单个数组包含所有对象，则必须在函数之外定义数组并定义 parseData 函数以返回一个对象，然后可以将其推入该数组。

const apartments = [];
const getRawData = async () => {
    try {
      await axios.get(url).then((res) => {
        const $ = cheerio.load(res.data);
        $('div[id="rezultatipretrage"] > div')
          .not('div[class="listitem artikal obicniArtikal  i index"]')
          .not('div[class="obicniArtikal"]')
          .each((index, element) => {
            $('span[class="prekrizenacijena"]').remove();
            const getLink = $(element)
              .find('div[class="naslov"] > a')
              .attr('href');

            ....

            //push the result of parseData into the array
            apartments.push(parsing.parseData(getLink, getDescription, getPrice, getPicture));


           //if your parsedata just returns an object created from its parameters,
           //you can get rid of the function and just do 
           //apartments.push({
           //  link: getLink,
           //  descr: getDescription,
           //  price: getPrice,
           //  picture: getPicture           
           //});
          });
      });
    } catch (error) {
      console.log(error);
    }
  };

重新定义parseData 只返回一个对象。虽然看起来没有必要，但拥有一个只返回其参数对象的函数。

exports.parseData = (getLink, getDescription, getPrice, getPicture) => {
  const apartment = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };
  return apartment;
};

Answer 3

你正在用 const 声明公寓。

const apartments = [];

所以它被设置为一个数组。但是随后您尝试将其更改为对象。

apartments = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };

常量不能被更新或声明。一旦你将它声明为一个数组。它只能作为一个数组保留。您可以推送到该数组，但不能将其更改为对象或任何其他数据类型。

在你的情况下，你可以直接将 const 公寓声明为一个对象。

const apartments = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };

您可以在此处阅读有关 var、let 和 const 的更多信息：https://www.freecodecamp.org/news/var-let-and-const-whats-the-difference/

添加基于 cmets 的示例。

const data = [];

const parseData = (getLink, getDescription, getPrice, getPicture) => {
    const apartments = {
        link: getLink,
        descr: getDescription,
        price: getPrice,
        picture: getPicture,
      };
    data.push(apartments)
    console.log(data);
};

data 不限于 parseData 函数，因此可以包含所有被推送给它的公寓对象。 data 数组的声明位置很大程度上取决于您的代码，并且可能也应该作为参数传递给 parseData 函数。

Answer 4

我看到的是您将变量apartments 分配为数组并将其声明为常量。然后，您尝试将变量重新分配给对象。

当您将变量分配为const 数组并尝试将其更改为对象时，您实际上是在更改对变量的引用，这是使用const 所不允许的。

const apartments = [];
  apartments = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };

我认为最简单的选项是将对象推入数组：

apartments.push({
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  });

或者在你即将推入数组时总是将对象分配给一个变量：

const apartments = [];
let apartment = {
    link: getLink,
    descr: getDescription,
    price: getPrice,
    picture: getPicture,
  };

apartments.push(apartment);