如何为多个元素调用javascript函数

Question

所以我从 w3schools.com 复制了这段代码：

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
* {box-sizing: border-box}
body {font-family: Verdana, sans-serif; margin:0}
.mySlides {display: none}
img {vertical-align: middle;}

/* Slideshow container */
.slideshow-container {
  max-width: 1000px;
  position: relative;
  margin: auto;
}

/* Next & previous buttons */
.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  padding: 16px;
  margin-top: -22px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
}

/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}

/* On hover, add a black background color with a little bit see-through */
.prev:hover, .next:hover {
  background-color: rgba(0,0,0,0.8);
}

/* Caption text */
.text {
  color: #f2f2f2;
  font-size: 15px;
  padding: 8px 12px;
  position: absolute;
  bottom: 8px;
  width: 100%;
  text-align: center;
}

/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}

/* The dots/bullets/indicators */
.dot {
  cursor: pointer;
  height: 15px;
  width: 15px;
  margin: 0 2px;
  background-color: #bbb;
  border-radius: 50%;
  display: inline-block;
  transition: background-color 0.6s ease;
}

.active, .dot:hover {
  background-color: #717171;
}

/* Fading animation */
.fade {
  -webkit-animation-name: fade;
  -webkit-animation-duration: 1.5s;
  animation-name: fade;
  animation-duration: 1.5s;
}

@-webkit-keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

@keyframes fade {
  from {opacity: .4} 
  to {opacity: 1}
}

/* On smaller screens, decrease text size */
@media only screen and (max-width: 300px) {
  .prev, .next,.text {font-size: 11px}
}
</style>
</head>
<body>

<div class="slideshow-container">

<div class="mySlides fade">
  <div class="numbertext">1 / 3</div>
  <img src="img_nature_wide.jpg" style="width:100%">
  <div class="text">Caption Text</div>
</div>

<div class="mySlides fade">
  <div class="numbertext">2 / 3</div>
  <img src="img_snow_wide.jpg" style="width:100%">
  <div class="text">Caption Two</div>
</div>

<div class="mySlides fade">
  <div class="numbertext">3 / 3</div>
  <img src="img_mountains_wide.jpg" style="width:100%">
  <div class="text">Caption Three</div>
</div>

<a class="prev" onclick="plusSlides(-1)">&#10094;</a>
<a class="next" onclick="plusSlides(1)">&#10095;</a>

</div>
<br>

<div style="text-align:center">
  <span class="dot" onclick="currentSlide(1)"></span> 
  <span class="dot" onclick="currentSlide(2)"></span> 
  <span class="dot" onclick="currentSlide(3)"></span> 
</div>

<script>
var slideIndex = 1;
showSlides(slideIndex);

function plusSlides(n) {
  showSlides(slideIndex += n);
}

function currentSlide(n) {
  showSlides(slideIndex = n);
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");
  if (n > slides.length) {slideIndex = 1}    
  if (n < 1) {slideIndex = slides.length}
  for (i = 0; i < slides.length; i++) {
      slides[i].style.display = "none";  
  }
  for (i = 0; i < dots.length; i++) {
      dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[slideIndex-1].style.display = "block";  
  dots[slideIndex-1].className += " active";
}
</script>

</body>
</html> 

这是制作图片库的代码。问题是当有多个名为 slideshow-gallery 的 div 时，javascript 将函数仅应用于一个 div。所以我的问题是如何为具有相同名称的多个 div 调用该函数？有任何想法吗？ 并提前致谢！

Answer 1

我不确定这是否与您正在寻找的内容 100% 完全相关。

但在 JavaScript 中至少有 3 种方法可以做到这一点。

let divs = document.getElementsByClassName("div");
let divs = document.getElementsByTagName("div");
let divs = document.querySelector("div");

所有 3 个方法都将返回完全相同的 HTMLCollection，包含所有选定的元素。

问题是，HTMLCollection 不是可迭代的。

不过，好消息。要转换它，您可以使用 Object.entries 方法：

Object.entries(divs).map(( object ) => {
    object[1].addEventListener("click", function() {    
        console.log("Hello " + this + " (" + this.innerHTML + ") from map method...");
    });
});

object[1] 是指向列表中“任何”对象的链接。这里只是为每个元素添加了一个点击事件。就你的情况而言，你可以在这里做任何你需要的事情。

进一步：这个tutorial about selecting multiple elements 我从中提取了这个例子可能会有用。