ScrollBooster

Enjoyable drag-to-scroll micro library (~2KB gzipped). Supports smooth content scroll via mouse/touch dragging, trackpad or mouse wheel. Zero dependencies.

Easy to setup yet flexible enough to support any custom scrolling logic.

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You can install it via npm or yarn package manager or via script tag:

`` bash
npm i scrollbooster
`

` bash
yarn add scrollbooster
`

` html

`

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The most simple setup with default settings:

` js
import ScrollBooster from 'scrollbooster';

new ScrollBooster({
viewport: document.querySelector('.viewport'),
scrollMode: 'transform'
});
`

Please note that in order to support IE11 you should replace arrow functions and string templates from code examples to supported equivalents or just use Babel.

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Option | Type | Default | Description
------ | ---- | ------- | -----------
viewport | DOM Node | null | Content viewport element (required)
content | DOM Node | viewport child element | Scrollable content element inside viewport
scrollMode | String | undefined | Scroll technique - via CSS transform or natively. Could be 'transform' or 'native'
direction | String | 'all' | Scroll direction. Could be 'horizontal', 'vertical' or 'all'
bounce | Boolean | true | Enables elastic bounce effect when hitting viewport borders
textSelection | Boolean | false | Enables text selection inside viewport
inputsFocus | Boolean | true | Enables focus for elements: 'input', 'textarea', 'button', 'select' and 'label'
pointerMode | String | 'all' | Specify pointer type. Supported values - 'touch' (scroll only on touch devices), 'mouse' (scroll only on desktop), 'all' (mobile and desktop)
friction | Number | 0.05 | Scroll friction factor - how fast scrolling stops after pointer release
bounceForce | Number | 0.1 | Elastic bounce effect factor
emulateScroll | Boolean | false | Enables mouse wheel/trackpad emulation inside viewport
preventDefaultOnEmulateScroll | String | false | Prevents horizontal or vertical default when emulateScroll is enabled (eg. useful to prevent horizontal trackpad gestures while enabling vertical scrolling). Could be 'horizontal' or 'vertical'.
lockScrollOnDragDirection | String | false | Detect drag direction and either prevent default mousedown/touchstart event or lock content scroll. Could be 'horizontal', 'vertical' or 'all'
dragDirectionTolerance | Number | 40 | Tolerance for horizontal or vertical drag detection
onUpdate | Function | noop | Handler function to perform actual scrolling. Receives scrolling state object with coordinates
onClick | Function | noop | Click handler function. Here you can, for example, prevent default event for click on links. Receives object with scrolling metrics and event object. Calls after each click in scrollable area
onPointerDown | Function | noop | mousedown/touchstart events handler
onPointerUp | Function | noop | mouseup/touchend events handler
onPointerMove | Function | noop | mousemove/touchmove events handler
onWheel | Function | noop | wheel event handler
shouldScroll | Function | noop | Function to permit or disable scrolling. Receives object with scrolling state and event object. Calls on pointerdown (mousedown, touchstart) in scrollable area. You can return true or false to enable or disable scrolling

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Method | Description
------ | -----------
setPosition | Sets new scroll position in viewport. Receives an object with properties x and y
scrollTo | Smooth scroll to position in viewport. Receives an object with properties x and y
updateMetrics | Forces to recalculate elements metrics. Useful for cases when content in scrollable area change its size dynamically
updateOptions | Sets option value. All properties from Options config object are supported
getState | Returns current scroll state in a same format as onUpdate
destroy | Removes all instance's event listeners

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` js
const viewport = document.querySelector('.viewport');
const content = document.querySelector('.scrollable-content');

const sb = new ScrollBooster({
viewport,
content,
bounce: true,
textSelection: false,
emulateScroll: true,
onUpdate: (state) => {
// state contains useful metrics: position, dragOffset, dragAngle, isDragging, isMoving, borderCollision
// you can control scroll rendering manually without 'scrollMethod' option:
content.style.transform = translate(
${-state.position.x}px,
${-state.position.y}px
);
},
shouldScroll: (state, event) => {
// disable scroll if clicked on button
const isButton = event.target.nodeName.toLowerCase() === 'button';
return !isButton;
},
onClick: (state, event, isTouchDevice) => {
// prevent default link event
const isLink = event.target.nodeName.toLowerCase() === 'link';
if (isLink) {
event.preventDefault();
}
}
});

// methods usage examples:
sb.updateMetrics();
sb.scrollTo({ x: 100, y: 100 });
sb.updateOptions({ emulateScroll: false });
sb.destroy();
``

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ScrollBooster has been tested in IE 11, Edge and other modern browsers (Chrome, Firefox, Safari).

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David DeSandro for his talk "Practical UI Physics".

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MIT License (c) Ilya Shubin