javascript - 构建 js 函数并在 HTML 中连接它时我做错了什么？

Question

我需要编写一个 js 函数来通过单击下拉元素来显示一些 HTML block 。它就是不去。你能帮帮我吗，我做错了什么？

function parameterOne(e) 
{
	e = event || window.event;
//	$('div.checkboxes').style.display = "none";
	$('div.checkboxes:first-child').style.display = "block";
	$('h4#kriterium').style.display = "block";
	return true;
}

/* Dropdown Button */
.dropbtn {
  background-color: #788bb6;
  color: white;
  padding: 10px 15px;
  font-size: 13px;
  cursor: pointer;
  border: none;
  border-radius: 3px;
}

/* Dropdown button on hover & focus
.dropbtn:hover, .dropbtn:focus {
  background-color: #2C3459;
} */

/* The container <div> - needed to position the dropdown content */
.dropdown {
  position: relative;
  display: inline-block;
}

/* Dropdown Content (Hidden by Default) */
.dropdown-content {
  display: none;
  position: absolute;
  background-color: #fff;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  z-index: 1;
}

/* Links inside the dropdown */
.dropdown-content a {
  color: #000;
  padding: 10px 15px;
  text-decoration: none;
  display: block;
  font-size: 13px;
}

/* Change color of dropdown links on hover */
.dropdown-content a:hover {background-color: #788bb6; color:#fff;}

/* Show the dropdown menu (use JS to add this class to the .dropdown-content container when the user clicks on the dropdown button) */
.show {display:block;}

/* Show the dropdown menu on hover */
.dropdown:hover .dropdown-content {display: block;}

label.checkbox {
	font-size: 13px;
	border: none;
}

div.checkboxes {
	margin-top: 15px;
	display: none;
}

h4#kriterium {
	display:none;
}

<div class="form">
					
					<div class="dropdown">
  <button onclick="dropdown()" class="dropbtn">Leads auswählen (sonst alle)</button>
  <div id="Lead" class="dropdown-content">
    <a href="#" onclick="parameterOne()" value="Click">Kriterium 1</a>
    <a href="#">Kriterium 2</a>
    <a href="#">Kriterium 3</a>
  </div>
</div>
<h4 id="kriterium">Kriterium 1</h4>
<div class="checkboxes">
<label class="checkbox"><input type="checkbox" value="1"> Wert 1</label>
<label class="checkbox"><input type="checkbox" value="2"> Wert 2</label>
<label class="checkbox"><input type="checkbox" value="3"> Wert 3</label>
</div>

我希望通过单击菜单中的第一个链接来显示第一个 div.checkboxes，但控制台显示以下错误:

Uncaught TypeError: Cannot set property 'display' of undefined
     at parameterOne (custom.js:49)
     at HTMLAnchorElement.onclick (VM7759 admin.html:156)

Answer 1

您正在混合普通 Javascript 和 jQuery。试试这个:

$('div.checkboxes:first-child').css('display', 'block')

更多信息请点击:https://api.jquery.com/css/

如果您想要 Javascript 方式，您应该使用 js 选择器(例如 querySelector 或 getElementsBy...)。 jQuery 返回它自己的元素拼写错误，但 Js 返回 HTMLCollection -> https://developer.mozilla.org/en-US/docs/Web/API/HTMLCollection