drag-scroll

A javascript library that offers ability of scrolling element by dragging.

Installation

$ npm install dragroll

Usage

Notice: Due to the package name occupation on npm, this package is named as "dragroll". However for usual use, it's recommended to import as "dragScroll", which will be more semantic and accurate.

Basic

import dragScroll from "dragroll"

dragScroll(draggable, scrollable)

API

function dragScroll(
    scrollable: HTMLElement,
    draggable: HTMLElement|null,
    options?:
    {
        movement?:
        {
            x?: [number, number]
            y?: [number, number]
            swapped?: boolean
        },
        constrained?: boolean
        destroy?: boolean,
        override?: boolean,
        avoid?: HTMLElement[],
        hooks?:
        {
            dragStart?: (event: MouseEvent, draggable: HTMLElement, draggable_data: DraggableData) => void|false
            drag?: (event: MouseEvent, draggable: HTMLElement, draggable_data: DraggableData) => void|false
            dragEnd?: (event: MouseEvent, draggable: HTMLElement, draggable_data: DraggableData) => void
        }
    },
): void

• scrollable

  The scrollable element. When drag occurs on draggable, scrollable scrolls correspondingly.

• draggable

  The draggable element. Drag on draggable triggers dragscroll action.
  When null, clear all dragscroll relations on passed scrollable.

• options

  Other options.

  • movement

    Movement constraint.

    • x, y

      Defines each drag_trigger_threshold and scroll_respond_vector, in form [number, number], in unit "px".

      drag_trigger_threshold: A quantum of dragging distance. When cursor drags out of per this quantum, trigger once scroll action.

      scroll_respond_vector: A quantum of scrolling distance. When scroll triggers, scroll this much distance.

    • swapped

      When true, swap dragscroll axis.

  • destroy

    When true, from target scrollable remove the dragscroll relation on target draggable.

  • override

    When true, in update override whole scrollable relations to only contain target relation.

  • constrained

    When true, dragscroll will only happen when cursor is inside scrollable.

  • avoid

    Dragscroll will not happen on those elements.

  • hooks

    Custom hooks.

    • dragStart

      Call when drag starts. Return false to prevent default behaviour.

    • drag

      Call on each drag move. Return false to prevent default behaviour.

    • dragEnd

      Call when drag ends.