GlobalEventHandlers.onwheel

The onwheel property of the GlobalEventHandlers mixin is an event handler that processes wheel events.

The wheel event fires when the user rotates the mouse (or other pointing device) wheel.

Note: Don't confuse onwheel with onscroll: onwheel handles general wheel rotation, while onscroll handles scrolling of an object's content.

Syntax

target.onwheel = functionRef;

Value

functionRef is a function name or a function expression. The function receives a WheelEvent object as its sole argument.

Examples

This example shows how to scale an element using the mouse (or other pointing device) wheel.

HTML

<div>Scale me with your mouse wheel.</div>

CSS

body {
  min-height: 100vh;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

div {
  width: 80px;
  height: 80px;
  background: #cdf;
  padding: 5px;
  transition: transform .3s;
}

JavaScript

function zoom(event) {
  event.preventDefault();

  if (event.deltaY < 0) {
    // Zoom in
    scale *= event.deltaY * -2;
  }
  else {
    // Zoom out
    scale /= event.deltaY * 2;
  }

  // Restrict scale
  scale = Math.min(Math.max(.125, scale), 4);

  // Apply scale transform
  el.style.transform = `scale(${scale})`;
}

let scale = 1;
const el = document.querySelector('div');
document.onwheel = zoom;

Result

Specifications

Specification
HTML Standard (HTML)
# handler-onwheel

Browser compatibility

BCD tables only load in the browser

See also