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Other References

CSSStyleDeclaration JS Conversion


WheelEvent deltaY Property

Example

Return whether the user scrolls up or down:

function myFunction(event) {
  var y = event.deltaY;
}
Try it Yourself »

Definition and Usage

The deltaY property returns a positive value when scrolling down, and a negative value when scrolling up, otherwise 0.

Note: This property is read-only.


Browser Support

Property
deltaY 31 yes 17 Not supported 18

Syntax

event.deltaY

Technical Details

Return Value: A Double, indicating the scrolling direction of the mouse wheel

Related Pages

HTML DOM reference: WheelEvent deltaX Property


More Examples

Example

Scroll inside a DIV to make it bigger/smaller:

function myFunction(event) {
  var y = event.deltaY;
  var currentSize = event.target.style.width;
  if (y > 0) {
    newSize = parseInt(currentSize) + 10;
  } else {
    newSize = parseInt(currentSize) - 10;
  }
  event.target.style.width = newSize + "px";
  event.target.style.height = newSize + "px";
}
Try it Yourself »