Javascript WheelEvent Tutorial
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WheelEvent is an interface representing for the events occurring when an user moves mouse wheel or similar equipment.

Browsers which support WheelEvent:

WheelEvent means sub-interface of MouseEvent. It will inherit all properties and methods of parent interface.

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Event | Description |
---|---|
wheel | The event occurs when the mouse wheel rolls up or down over an element |
The properties of WheelEvent:
Property | Description |
---|---|
deltaX | Returns the horizontal scroll amount of a mouse wheel (x-axis) |
deltaY | Returns the vertical scroll amount of a mouse wheel (y-axis) |
deltaZ | Returns the scroll amount of a mouse wheel for the z-axis |
deltaMode | Returns a number that represents the unit of measurements for delta values (DOM_DELTA_PIXEL, DOM_DELTA_PIXEL, DOM_DELTA_PAGE) |
Constants:
Constant | Value | Description |
DOM_DELTA_PIXEL | 0 | Measuring unit of delta is pixels. |
DOM_DELTA_LINE | 1 | Measuring unit of delta is lines. |
DOM_DELTA_PAGE | 2 | Measuring unit of delta is pages. |
Example with WheelEvent:

wheelevents-example.html
<!DOCTYPE html> <html> <head> <title>WheelEvent Example</title> <script src="wheelevents-example.js"></script> </head> <body> <h3>WheelEvent example</h3> <div style="font-size:12px; padding:5px; border:1px solid #ccc;" onwheel="wheelHandler(event)"> Hello Everyone! <div> </body> </html>
wheelevents-example.js
function wheelHandler(evt) { var fontSize = evt.target.style.fontSize;// 12px, 13px,... var value = Number(fontSize.substr(0, fontSize.length-2)); // 12, 13,.. // Scrolling up if (evt.deltaY < 0) { if(value < 50) { value++; } } // Scrolling down if(evt.deltaY > 0) { if(value > 5) { value--; } } evt.target.style.fontSize = value+"px"; }