js数组不返回特定文本的索引值，即使文本存在

neekobn8 于 2021-09-08 发布在 Java

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对js来说相当陌生。我有一个html表格，列的顺序是：大陆，国家，等等。。。到目前为止，我已经有了工作代码，可以读取html表，为所有国家创建一个数组，然后删除重复项。我还有一个数组，它在html表中为countries数组的每个元素查找大陆。
我的问题是，我似乎无法查找大陆数组中的所有索引以获得某个值（例如“非洲”）。这是我的密码：

//Step 1: create an array to hold each country's continent. The 'countries' array was 
previously created. 

   var continents = [];
   for (const element of countries){
     console.log(element);

      var contin = []; 
      for (j = 0 ; j < data.rows.length; j++){
         if (data.rows[j].cells[1].innerHTML.indexOf(element) >= 0) 
         contin.push(data.rows[j].cells[0].innerHTML);
         }
         continents.push(contin);
}

//Step 2: Create a function that can look up all indexes in the continents array for a certain value.
        function getAllIndexes(arr, val) {
          var indexes = [], i;
          for(i = 0; i < arr.length; i++)
              if (arr[i] === val)
              indexes.push(i);
          return indexes;
        }

//Step 3: Run the function to get all index values where continents array = "Africa"
         indexesAfrica = getAllIndexes(continents, "Africa");
         alert(indexesAfrica);

当我运行该函数时，它返回一个空白。我已经在其他阵列上测试了该函数，它可以正常工作。例如，此代码返回“1,3”的正确索引：

var funArr = ["test", "Africa", "Hello","Africa"];
indexesAfrica = getAllIndexes(funArr, "Africa");
alert(indexesAfrica);

这让我觉得我的大陆阵列有问题？当我发出警报（大陆）时，大陆阵列显示正确的阵列项目列表，但我似乎无法在其中查找任何内容。思想？

Arrays JavaScript indexing Lookup

来源：https://stackoverflow.com/questions/68330926/js-array-not-returning-index-values-of-specific-text-even-though-text-exists

1条答案

按热度按时间

cotxawn71#

我本打算把这作为一个评论，但它似乎可以解决你的情况，也许可以帮助你学到一些东西。为什么将它们作为两个独立的阵列？它的伸缩性不是很好。如果你对你的国家阵列进行排序，你将失去与欧洲大陆的联系。最好将它们耦合在一组对象中，这样很容易过滤（比如，如果您只想显示非洲的国家）。

let countries = ["Algeria", "Angola", "Benin", "Botswana", "Burkina Faso", "Burundi", "Cameroon", "Cape Verde", "USA"]
let data = document.querySelector('table');

let globe = countries.map(country => { // using map, we can transform each incoming country into a country/continent object
  let continent = 'N/A'; // just so we have somethign in case we dont find a continent
  [...data.rows].forEach(row => { // data is the table, rows are the <tr> tags, but we need to make it iterable for the loop, so we wrap it in a spread [...] 
    if (row.cells[1].innerText.trim() === country) continent = row.cells[0].innerText.trim();
  })
  return { country: country, continent: continent}; // we return an object back to our map
});
console.log(globe)

//Step 2: Run the function to get all index values where continents array = "Africa"

const africanCountries = globe.filter(e => e.continent === "Africa").map(e => e.country);
console.log(africanCountries)

<table>
  <tr><td>Africa</td><td>Algeria</td></tr>
  <tr><td>Africa</td><td>Angola</td></tr>
  <tr><td>Africa</td><td>Benin</td></tr>
  <tr><td>North America</td><td>USA</td></tr>
  <tr><td>Africa</td><td>Botswana</td></tr>
  <tr><td>Africa</td><td>Burkina Faso</td></tr>
  <tr><td>Africa</td><td>Faso</td></tr>
  <tr><td>Africa</td><td>Burundi</td></tr>
  <tr><td>Africa</td><td>Cameroon</td></tr>
  <tr><td>Africa</td><td>Cape Verde</td></tr>
</table>

更新：要添加lat和long，可以点击map（）中的索引

let globe = countries.map((country, index) => { // using map, we can transform each incoming country into a country/continent object
  let continent = 'N/A'; // just so we have somethign in case we dont find a continent
  [...data.rows].forEach(row => { // data is the table, rows are the <tr> tags, but we need to make it iterable for the loop, so we wrap it in a spread [...] 
    if (row.cells[1].innerText.trim() === country) continent = row.cells[0].innerText.trim();
  })
  return { 
     country: country, 
     continent: continent,
     lat: countryLat[index],
     long: countryLong[index]
   }; // we return an object back to our map
});

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js数组不返回特定文本的索引值，即使文本存在

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