Zoom Gesture

npm library that detects zoom gesture (mouse wheel or pinch) on DOM node

Example

import ZoomGesture from 'zoom-gesture';
 
const zoomNode = document.querySelector('.zoom');
const zoomHandler = new ZoomGesture({
  element: zoomNode,
  minScale: 1,
  maxScale: 2,
  // read more about options below
});
const fn = zoom => { /* some things with zoom */ };
 
zoomHandler.on('change', fn);
zoomHandler.init();
// read more about methods below

Options

element

DOM node where you need to detect zoom gesture.

Default: window.

initScale

Init value of scale.

Default: 1.

wheelScaleSize

Amount of pixels that user must scroll by mouse or touchpad to change scale value by 1.

Default: 300.

touchScaleSize

Amount of pixels that user must move (pinch) by touch pointers (fingers, etc) using to change scale value by 1.

Default: undefined.

Note: there is no default value, because default behaviour is slightly different.

By default when user starts to do pinch gesture, the library counts distance between touch points and when it doubles — the library increases scale value by 1 (when it is tripled — by 2, etc).

minScale

Minimum value of scale.

Default: undefined.

Note: undefined value (or any other non-numeric) value means that scale value may be negative.

maxScale

Maximum value of scale.

Default: undefined.

Methods

init

Use it to initialize all listeners.

destroy

Use it to remove all listeners.

setScale

Use it to set scale value manually, it you need it.

Note: the library does not check value that you set using this method by range of possible values (that you can set by minScale and maxScale), but it triggers listeners of change event.

Arguments:

• scale (numeric).

on

Use it to add listeners for the library events.

Right now there is only one event — change. Read about it below.

Arguments:

• event (string);
• fn (func).

off

Use it to remove listeners for the library events.

Right now there is only one event — change. Read about it below.

Arguments:

• event (string);
• fn (func).

Events

change

Handlers for this event are called when scale value is changed by user's zoom gesture.

Parameters passed to handler:

• scale (numeric).

Why?

Sometimes I need to implement some things where I need to detect zoom gesture and do something depends on it. For example, image editor where you can change zoom of selected image.