In this tutorial we will check if the bottom of the page is visible to the user. We can achieve this by using the height of the window and the height of the scrollingwindow. To write this code we need to know three methods of JavaScript as follows:
scrollY - It is a read-only property of the window and returns the number of pixels the document has for vertical scrolling.
window.scrollY
scrollHeight -It is an HTML DOM element and a read-only property of the window. It returns the height of the element's content, including invisible content.
element.scrollHeight
clientHeight - This is also a read-only property that returns the visual height of the element in pixels, including padding, but not borders, scrollbars, or margins.
element.clientHeight window.clientHeight
Note - All three methods above measure the value of an element in pixels.
Syntax
The following is the syntax for the condition to be checked if the bottom of the page is visible.
document.documentElement.clientHeight + window.scrollY >=(document.documentElement.scrollHeight ||document.documentElement.clientHeight);
If the above conditions are true, the bottom of the page will be visible.
Method
We check that clientHeight and scrollY are greater than or equal to scrollHeight or clientHeight. If this condition is true, the bottom of the page will be visible. Therefore, we define a function that returns true if the condition is met.
Example
Using the clientHeight property of documentElement>
In the following program, we Check if the bottom of the page is visible. We use the clientHeight property of documentElement to check the conditions defined in the syntax section.
<!DOCTYPE html>
<html>
<head>
<title>Example - Bottom Visible JavaScript</title>
</head>
<body>
<div style="margin-bottom:100px;">
<h3 id="Checking-if-bottom-of-page-is-visible">Checking if bottom of page is visible</h3>
<p id = "bottom"> Is bottom of the Page visible?<br></p>
</div>
<div> You reached to the bottom of the page.</div>
<script>
const bottomVisible = () =>
document.documentElement.clientHeight + window.scrollY >=
(document.documentElement.scrollHeight ||
document.documentElement.clientHeight);
console.log(bottomVisible());
document.getElementById("bottom").innerHTML += bottomVisible()
</script>
</body>
</html>In the above code, we compare two values, one is the sum of client height and scrollY, and the other is the OR operation of scroll height and client height. When the sum of the client height and scrollY is greater than or equal to the OR operation of the scroll height and the client height, the result value is true, indicating that the bottom of the page is visible.
Example
Using the clientHeight property of the window interface
In the following program, we Check if the bottom of the page is visible or not. We use the clientHeight property of the window interface to check the conditions defined in the syntax section.
<!DOCTYPE html>
<html>
<head>
<title>Example - Bottom Visible JavaScript</title>
</head>
<body>
<div style="margin-bottom:100px;">
<h3 id="Checking-if-bottom-of-page-is-visible">Checking if bottom of page is visible</h3>
<p id = "bottom"> Is bottom of the Page visible?<br></p>
</div>
<div> You reached to the bottom of the page.</div>
<script>
const bottomVisible = () =>
window.innerHeight + window.scrollY >=(document.documentElement.scrollHeight || window.innerHeight);
console.log(bottomVisible());
document.getElementById("bottom").innerHTML += bottomVisible()
</script>
</body>
</html>Example
The bottom of the page is not visible
In the following program, we set the bottom margin of the div very high so that the bottom of the page Invisible.
<html>
<head>
<title>Example - Bottom Visible JavaScript</title>
</head>
<body>
<div style="margin-bottom:2500px;">
<h3 id="The-bottom-of-page-not-visible">The bottom of page not visible</h3>
<p id = "bottom"> Is bottom of the Page visible?<br></p>
<p id> <br> Please scroll down to reach the bottom...</p>
</div>
<div> You reached to the bottom of the page.</div>
<script>
const bottomVisible = () =>
window.clientHeight + window.scrollY >=(document.documentElement.scrollHeight || window.clientHeight);
console.log(bottomVisible());
document.getElementById("bottom").innerHTML += bottomVisible()
</script>
</body>
</html>The above is the detailed content of How to return true if bottom of page is visible using JavaScript?. For more information, please follow other related articles on the PHP Chinese website!
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