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javascript - 在用于制作过滤器的 javascript 代码中键入错误

问题描述

我改变了我的方法并用按钮制作了一个选择器，所以我这样做：

此代码的目的是通过单击显示与一个按钮相对应的图像，因为知道有几个具有不同名称的图像 HTML 代码：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>repl.it</title>
<link href="index.css" rel="stylesheet" type="text/css"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
</head>
<body>
    <script src="index.js"></script>
    <div id="btnconteneur">
        <button class="btn active" onclick="filter('all')">Show all</button>
        <button class="btn" onclick="filter('AttributionCodeConfidentiel')">Attribution Code confidentiel</button>
        <button class="btn" onclick="filter('bis')">Bis</button>
    </div>
    <div class="conteneur">
       <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel.png" alt="" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201706.png" alt="201706" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201707.png" alt="201707" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201708.png" alt="201708" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201709.png" alt="201709" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201710.png" alt="201710" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201711.png" alt="201711" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201712.png" alt="201712" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201801.png" alt="201801" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201802.png" alt="201802" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201803.png" alt="201803" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201804.png" alt="201804" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201805.png" alt="201805" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201806.png" alt="201806" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201807.png" alt="201807" /></div>
        <div class=" filtre AttributionCodeConfidentiel"><img src="test/AttributionCodeConfidentiel_201808.png" alt="201808" /></div>
        <div class=" filtre bis"><img src="test/bis.png" alt="" /></div>
        <div class=" filtre bis"><img src="test/bis_201706.png" alt="201706" /></div>
        <div class=" filtre bis"><img src="test/bis_201707.png" alt="201707" /></div>
        <div class=" filtre bis"><img src="test/bis_201708.png" alt="201708" /></div>
        <div class=" filtre bis"><img src="test/bis_201709.png" alt="201709" /></div>
        <div class=" filtre bis"><img src="test/bis_201710.png" alt="201710" /></div>
        <div class=" filtre bis"><img src="test/bis_201711.png" alt="201711" /></div>
        <div class=" filtre bis"><img src="test/bis_201801.png" alt="201801" /></div>
        <div class=" filtre bis"><img src="test/bis_201802.png" alt="201802" /></div>
        <div class=" filtre bis"><img src="test/bis_201803.png" alt="201803" /></div>
        <div class=" filtre bis"><img src="test/bis_201804.png" alt="201804" /></div>
        <div class=" filtre bis"><img src="test/bis_201805.png" alt="201805" /></div>
        <div class=" filtre bis"><img src="test/bis_201806.png" alt="201806" /></div>
        <div class=" filtre bis"><img src="test/bis_201807.png" alt="201807" /></div>
        <div class=" filtre bis"><img src="test/bis_201808.png" alt="201808" /></div>
</body>
</html>

和我的 javascript ：

function filter(c) {
  var x, i;
  x = document.getElementsByClassName("filtre");
  if (c == "all") c = "";
  // Add the "show" class (display:block) to the filtered elements, and remove the "show" class from the elements that are not selected
  for (i = 0; i < x.length; i++) {
    w3RemoveClass(x[i], "show");
    if (x[i].className.indexOf(c) > -1) w3AddClass(x[i], "show");
  }
}

// Show filtered elements
function w3AddClass(element, name) {
  var i, arr1, arr2;
  arr1 = element.className.split(" ");
  arr2 = name.split(" ");
  for (i = 0; i < arr2.length; i++) {
    if (arr1.indexOf(arr2[i]) == -1) {
      element.className += " " + arr2[i];
    }
  }
}

// Hide elements that are not selected
function w3RemoveClass(element, name) {
  var i, arr1, arr2;
  arr1 = element.className.split(" ");
  arr2 = name.split(" ");
  for (i = 0; i < arr2.length; i++) {
    while (arr1.indexOf(arr2[i]) > -1) {
      arr1.splice(arr1.indexOf(arr2[i]), 1);
    }
  }
  element.className = arr1.join(" ");
}

// Add active class to the current control button (highlight it)
var btnContainer = document.getElementById('btnconteneur');
var btns = btnContainer.getElementsByClassName("btn");
for (var i = 0; i < btns.length; i++) {
  btns[i].addEventListener("click", function() {
    var current = document.getElementsByClassName("active");
    current[0].className = current[0].className.replace(" active", "");
    this.className += " active";
  });
}

一切似乎都很好，但是当我运行时出现错误：

类型错误：document.getElementById(...) 为空

而且我不明白为什么出现这个错误:(

标签： javascripthtmlfunction

解决方案

将您的脚本index.js包含在body标记的开头，它会被执行，当它运行时var btnContainer = document.getElementById('btnconteneur');，它找不到element并返回null。

因此，您应该index.js在 body 标记结束之前包含该标记，以便在执行脚本时所有元素都可用。

<script src="index.js"></script>
</body>

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