momentum.js

momenutm.js is a small (plainly written) JavaScript plugin, giving you the ability to add a "throw momentum effect" to anything displayed on your webpage. It can be a handy alternative to the Draggable extension of the greensock animation framework. Besides desktop devices it also works for mobile and touch devices.

Installation

To use momentum.js you have to include the momentum.js file from the dist folder. If your server supports serving compressed files you can also put the compressed gz file in the same directory as the js file. This improves the loading time by more than 50%. It also comes as a npm module:

npm install --save momentum.js

Usage

You can use this package by simply including it like this:

import { Draggable, Handler, Rotatable } from 'momentum.js';

How to use the Draggable

The Draggable component allows your elements to be dragged around.

new momentum.Draggable(element, config);

This example shows how to create a basic draggable element:

new momentum.Draggable(dragElement, {
  container: containerElement,
  containerBounds: true,
  resizeUpdate: true,
  autoAnchor: true
});

Some Draggable Demos

http://momentum.davide-perozzi.de/

The Draggable configuration

Option	Type	Default	Description
container	Element	null	Container of the draggable element. Also the target for the "drag events"
elementBounds	Element|string	null	Determines if the bounds of a element should be used. As a shortcut you can pass 'container' or 'parent' as a string
bounds	Object	null	Set the bounds manually {x: number y: number, width: number, height: number}
autoAnchor	boolean	false	Determines if the anchor should be set on the start position the user has clicked
anchorX	number	0.5	The anchor point on the horizontal axis.
anchorY	number	0.5	The anchor point on the vertical axis.
threshold	number	5	The minimum velocity the element needs to reach to trigger the throw animation
restitution	number	0	The bounciness of the element if it hits the bounds. This will be multiplicated with the velocity. You can use negative values to let the element bounce out of the bounds. Numbers from -1 to 1 are valid.
friction	number	0.035	The friction of the element. Lower values make the elements decelerate longer. Numbers from 0 to 1 are valid
offsetFriction	number	0.1	The friction used out of bounds. This will be included in the calculations if you used a negative restitution. Numbers from 0 to 1 are valid
maxVelocity	number	70	The maximum velocity the element can reach. Numbers greater than 0 are valid.
resizeUpdate	boolean	false	Determines whether the draggable should be updated automatically after the browser is resized.
lockAxis	Object	null	Locked axis will be excluded from the translation. For example: {x: false, y: true}. This will lock the y axis.
onUp	Function	null	Callback which will be called if the user released the element.
onDown	Function	null	Callback which will be called if the user hits the element before the drag. Whether you return true or false determimes if the drag will be accepted. If you want to preserve the default behaviour you should return the "hit" parameter. Parameter list: hit, cursorX, cursorY, elementX, elementY, elementWidth, elementHeight
onMove	Function	null	This will be triggered before the element is going to be moved. At this point the element does not have the latest translation. You can return an coordinate object like "{x: number, y: number}" to manipulate the position of the element. Parameter list: posX, posY, velX, velY.
onTranslate	Function	null	This will be called if the translation settled. Parameter list: elementX, elementY, elementWidth, elementHeight, elementBounds
preventMove	Function	null	A function which needs to return wheter true or false to prevent the movement. This can be useful to add a move threshold. Paramter list: movedX, movedY, isTouchDevice

License

momentum.js is open-sourced software licensed under the MIT license.