Dados muchos elementos dentro del DOM, la tarea es averiguar qué elemento se está desplazando actualmente usando JavaScript.
Enfoque: este problema se puede resolver fácilmente usando JavaScript. Agregaremos el detector de eventos ‘scroll’ a todos los elementos requeridos. El evento de desplazamiento se activa cada vez que se desplaza un elemento en particular. Por lo tanto, podemos averiguar fácilmente qué elemento se está desplazando con la ayuda de este.
Ejemplo: en este ejemplo, creamos dos elementos desplazables y agregamos el detector de eventos ‘scroll’ a ambos. Tan pronto como se desplaza cualquiera de los elementos, se activa el evento de desplazamiento de ese elemento en particular.
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport"
content="width=device-width, initial-scale=1.0" />
<title>How to identify which element
scroll is being used using JavaScript?</title>
<style>
h1 {
color: #2f8d46;
font-weight: bold;
margin: 40px;
}
#first {
height: 200px;
width: 400px;
overflow-y: scroll;
margin: 40px;
}
#second {
margin: 40px;
height: 200px;
width: 400px;
overflow-y: scroll;
}
#scrolled {
margin: 40px;
}
</style>
</head>
<body>
<h1>GeeksforGeeks</h1>
<!--First element-->
<div id="first">
<h2>First element</h2>
<p>
JavaScript is a lightweight, cross-platform
and interpreted scripting language. It is well-known
for the development of web pages, many non-browser
environments also use it. JavaScript can be used for
Client-side developments as well as Server-side
developments. JavaScript contains a standard library
of objects, like Array, Date, and Math, and a core
set of language elements like operators, control
structures, and statements.
History of JavaScript: It was created in 1995
by Brendan Eich while he was an engineer at Netscape.
It was originally going to be named LiveScript but
was renamed. Unlike most programming languages,
the JavaScript language has no concept of input
or output. It is designed to run as a scripting
language in a host environment, and it is up to
the host environment to provide mechanisms for
communicating with the outside world. The most
common host environment is the browser.
</p>
</div>
<!--Second element-->
<div id="second">
<h2>Second element</h2>
<p>
JavaScript is a lightweight, cross-platform
and interpreted scripting language. It is well-known
for the development of web pages, many non-browser
environments also use it. JavaScript can be used for
Client-side developments as well as Server-side
developments. JavaScript contains a standard library
of objects, like Array, Date, and Math, and a core
set of language elements like operators, control
structures, and statements.
History of JavaScript: It was created in 1995
by Brendan Eich while he was an engineer at Netscape.
It was originally going to be named LiveScript but
was renamed. Unlike most programming languages,
the JavaScript language has no concept of input
or output. It is designed to run as a scripting
language in a host environment, and it is up to
the host environment to provide mechanisms for
communicating with the outside world. The most
common host environment is the browser.
</p>
</div>
<div id="scrolled">
<h3>Element being scrolled: <span id="result"></span></h3>
</div>
<script>
<!--Selecting required elements from the DOM-->
const first = document.querySelector("#first");
const second = document.querySelector("#second");
const result = document.querySelector("#result");
<!--Adding the scroll event listener-->
first.addEventListener("scroll", () => (result.textContent = "First"));
second.addEventListener("scroll", () => (result.textContent = "Second"));
</script>
</body>
</html>
Producción:
