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Drag to scroll

Written byPhuoc Nguyen
Category
Level 3 — Advanced
Created
20 Apr, 2020
Last updated
16 Sep, 2021
Contributors
jmidtlyng
User often uses the mouse to scroll in a scrollable container. In addition to that, some applications also allow user to scroll by dragging the element. You can see that feature implemented in a PDF viewer, Figma and many more.
This post shows you a simple way to archive that feature with vanilla JavaScript.
Assume that we have a scrollable container as below:
<div id="container" class="container">...</div>
The element must have at least two CSS properties:
.container {
cursor: grab;
overflow: auto;
}
The `cursor: grab` indicates that the element can be clicked and dragged.

Scroll to given position

As long as the element is scrollable, we can scroll it to given position by setting the `scrollTop` or `scrollLeft` property:
const ele = document.getElementById('container');
ele.scrollTop = 100;
ele.scrollLeft = 150;

Drag to scroll

The implementation is quite straightforward. By using the similar technique in the Make a draggable element post, we start with handling the `mousedown` event which occurs when user clicks the element:
let pos = { top: 0, left: 0, x: 0, y: 0 };

const mouseDownHandler = function (e) {
pos = {
// The current scroll
left: ele.scrollLeft,
top: ele.scrollTop,
// Get the current mouse position
x: e.clientX,
y: e.clientY,
};

document.addEventListener('mousemove', mouseMoveHandler);
document.addEventListener('mouseup', mouseUpHandler);
};
Tip
`pos` stores the current scroll and mouse positions. When user moves the mouse, we calculate how far it has been moved, and then scroll to the element to the same position:
const mouseMoveHandler = function (e) {
// How far the mouse has been moved
const dx = e.clientX - pos.x;
const dy = e.clientY - pos.y;

// Scroll the element
ele.scrollTop = pos.top - dy;
ele.scrollLeft = pos.left - dx;
};
Good practice
As you see above, the `left`, `top`, `x`, and `y` properties are related to each other. It's better to encapsulate them in a single variable `pos` instead of creating four variables.
Last but not least, we can improve the user experience by setting some CSS properties when user starts moving the mouse:
const mouseDownHandler = function(e) {
// Change the cursor and prevent user from selecting the text
ele.style.cursor = 'grabbing';
ele.style.userSelect = 'none';
...
};
These CSS properties are reset when the mouse is released:
const mouseUpHandler = function () {
document.removeEventListener('mousemove', mouseMoveHandler);
document.removeEventListener('mouseup', mouseUpHandler);

ele.style.cursor = 'grab';
ele.style.removeProperty('user-select');
};

Use cases

Hopefully you love the following demo!

Demo

See also

Questions? 🙋

Do you have any questions? Not just about this specific post, but about any topic in front-end development that you'd like to learn more about? If so, feel free to send me a message on Twitter or send me an email. You can find them at the bottom of this page.
I have a long list of upcoming posts, but your questions or ideas for the next one will be my top priority. Let's learn together! Sharing knowledge is the best way to grow 🥷.

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Phước Nguyễn