/ Drag Drop

Beautiful, accessible drag and drop for lists with React.js

Beautiful, accessible drag and drop for lists with React.js

react-beautiful-dnd

Beautiful, accessible drag and drop for lists with React.js.

Examples 🎉

See how beautiful it is for yourself - have a play with the examples!

Core characteristics:

  • beautiful, natural movement of items
  • clean and powerful api which is simple to get started with
  • unopinionated styling
  • no creation of additional wrapper dom nodes - flexbox and focus management friendly!
  • plays well with existing interactive nodes such as anchors
  • state driven dragging - which allows for dragging from many input types, including programatic dragging. Currently only mouse and keyboard dragging are supported

Not for everyone

There are a lot of libraries out there that allow for drag and drop interactions within React. Most notable of these is the amazing react-dnd. It does an incredible job at providing a great set of drag and drop primitives which work especially well with the wildly inconsistent html5 drag and drop feature. react-beautiful-dnd is a higher level abstraction specifically built for vertical and horizontal lists. Within that subset of functionality react-beautiful-dnd offers a powerful, natural and beautiful drag and drop experience. However, it does not provide the breadth of functionality offered by react-dnd. So this library might not be for you depending on what your use case is.

Still young!

This library is still fairly new and so there is a relatively small feature set. Be patient! Things will be moving rather quickly!

Currently supported feature set

  • vertical lists ↕
  • horizontal lists ↔
  • multiple independent lists on the one page
  • mouse 🐭 and keyboard 🎹 dragging
  • independent nested lists (list can be a child of another list, but you cannot drag items from the parent list into a child list)
  • flexible height items (the draggable items can have different heights)
  • custom drag handle (you can drag a whole item by just a part of it)
  • the vertical list can be a scroll container (without a scrollable parent) or be the child of a scroll container (that also does not have a scrollable parent)

Basic usage example

This is a simple reorderable list. You can play with it on webpackbin

basic example

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
import { DragDropContext, Droppable, Draggable } from 'react-beautiful-dnd';

// fake data generator
const getItems = count =>
  Array.from({ length: count }, (v, k) => k).map(k => ({
    id: `item-${k}`,
    content: `item ${k}`,
  }));

// a little function to help us with reordering the result
const reorder = (list, startIndex, endIndex) => {
  const result = Array.from(list);
  const [removed] = result.splice(startIndex, 1);
  result.splice(endIndex, 0, removed);

  return result;
};

// using some little inline style helpers to make the app look okay
const grid = 8;
const getItemStyle = (draggableStyle, isDragging) => ({
  // some basic styles to make the items look a bit nicer
  userSelect: 'none',
  padding: grid * 2,
  marginBottom: grid,

  // change background colour if dragging
  background: isDragging ? 'lightgreen' : 'grey',

  // styles we need to apply on draggables
  ...draggableStyle,
});
const getListStyle = isDraggingOver => ({
  background: isDraggingOver ? 'lightblue' : 'lightgrey',
  padding: grid,
  width: 250,
});

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      items: getItems(10),
    };
    this.onDragEnd = this.onDragEnd.bind(this);
  }

  onDragEnd(result) {
    // dropped outside the list
    if (!result.destination) {
      return;
    }

    const items = reorder(
      this.state.items,
      result.source.index,
      result.destination.index
    );

    this.setState({
      items,
    });
  }

  // Normally you would want to split things out into separate components.
  // But in this example everything is just done in one place for simplicity
  render() {
    return (
      <DragDropContext onDragEnd={this.onDragEnd}>
        <Droppable droppableId="droppable">
          {(provided, snapshot) => (
            <div
              ref={provided.innerRef}
              style={getListStyle(snapshot.isDraggingOver)}
            >
              {this.state.items.map(item => (
                <Draggable key={item.id} draggableId={item.id}>
                  {(provided, snapshot) => (
                    <div>
                      <div
                        ref={provided.innerRef}
                        style={getItemStyle(
                          provided.draggableStyle,
                          snapshot.isDragging
                        )}
                        {...provided.dragHandleProps}
                      >
                        {item.content}
                      </div>
                      {provided.placeholder}
                    </div>
                  )}
                </Draggable>
              ))}
            </div>
          )}
        </Droppable>
      </DragDropContext>
    );
  }
}

// Put the thing into the DOM!
ReactDOM.render(<App />, document.getElementById('app'));

Physicality

The core design idea of react-beautiful-dnd is physicality: we want users to feel like they are moving physical objects around

Application 1: no instant movement

It is a fairly standard drag and drop pattern for things to disappear and reappear in response to the users drag. For a more natural drag we animate the movement of items as they need to move out of the way while dragging to more clearly show a drags effect. We also animate the drop of an item so that it animates into its new home position. At no point is an item instantly moved anywhere — regardless of whether it is dragging or not.

Application 2: knowing when to move

It is quite common for drag and drop interactions to be based on the position that user started the drag from.

In react-beautiful-dnd a dragging items impact is based on its centre of gravity — regardless of where a user grabs an item from. A dragging items impact follows similar rules to a set of scales ⚖️. Here are some rules that are followed to allow for a natural drag experience even with items of flexible height:

  • A list is dragged over when the centre position of a dragging item goes over one of the boundaries of the list
  • A resting drag item will move out of the way of a dragging item when the centre position of the dragging item goes over the edge of the resting item. Put another way: once the centre position of an item (A) goes over the edge of another item (B), B moves out of the way.

Application 3: no drop shadows

Drop shadows are useful in an environment where items and their destinations snap around. However, with react-beautiful-dnd it should be obvious where things will be dropping based on the movement of items. This might be changed in the future - but the experiment is to see how far we can get without any of these affordances.

Application 4: maximise interactivity

react-beautiful-dnd works really hard to avoid as many periods of non-interactivity as possible. The user should feel like they are in control of the interface and not waiting for an animation to finish before they can continue to interact with the interface. However, there is a balance that needs to be made between correctness and power in order to make everybody's lives more sane. Here are the only situations where some things are not interactive:

  1. From when a user cancels a drag to when the drop animation completes. On cancel there are lots of things moving back to where they should be. If you grab an item in a location that is not its true home then the following drag will be incorrect.
  2. Starting a drag on an item that is animating its own drop. For simplicity this is the case - it is actually quite hard to grab something while it is animating home. It could be coded around - but it seems like an edge case that would add a lot of complexity.

Keep in mind that these periods of inactivity may not always exist.

Application 5: no drag axis locking

For now, the library does not support drag axis locking (aka drag rails). This is where the user is restricted to only dragging along one axis. The current thinking is this breaks the physical metaphore we are going for and sends a message to the user that they are interacting with a piece of software rather than moving physical objects around. It is possible to ensure that a user can only drop in a single list by using props type and isDropEnabled. You can also do some visual treatment to the list onDragStart to show the user that this is the only place they can interact with.

Sloppy clicks and click blocking 🐱🎁

When a user presses the mouse down on an element, we cannot determine if the user was clicking or dragging. Also, sometimes when a user clicks they can move the cursor slightly — a sloppy click. So we only start a drag once the user has moved beyond a certain distance with the mouse down (the drag threshold) — more than they would if they where just making a sloppy click. If the drag threshold is not exceeded then the user interaction behaves just like a regular click. If the drag threshold is exceeded then the interaction will be classified as a drag and the standard click action will not occur.

This allows consumers to wrap interactive elements such as an anchor and have it be both a standard anchor as well as a draggable item in a natural way.

(🐱🎁 is a schrodinger's cat joke)

Focus management

react-beautiful-dnd does not create any wrapper elements. This means that it will not impact the usual tab flow of a document. For example, if you are wrapping an anchor tag then the user will tab to the anchor directly and not an element surrounding the anchor. Whatever element you wrap will be given a tab-index to ensure that users can tab to the element to perform keyboard dragging.

Accessibility

Traditionally drag and drop interactions have been exclusively a mouse or touch interaction. This library ships with support for drag and drop interactions using only a keyboard. This enables power users to drive their experience entirely from the keyboard. As well as opening up these experiences to users who would have been excluded previously.

In addition to supporting keyboard, we have also audited how the keyboard shortcuts interact with standard browser keyboard interactions. When the user is not dragging they can use their keyboard as they normally would. While dragging we override and disable certain browser shortcuts (such as tab) to ensure a fluid experience for the user.

Shortcuts

Currently the keyboard handling is hard coded. This might be changed in the future to become customisable. Here is the existing keyboard mapping:

  • tab tab ↹ - standard browser tabbing will navigate through the Droppable's. The library does not do anything fancy with tab while users are selecting. Once a drag has started, tab is blocked for the duration of the drag.
  • spacebar space - lift a focused Draggable. Also, drop a dragging Draggable where the drag was started with a spacebar.
  • Up arrow - move a Draggable that is dragging backward in a vertical list
  • Down arrow - move a Draggable that is dragging forward in a vertical list
  • Left arrow - move a Draggable that is dragging backward in a horizontal list
  • Right arrow - move a Draggable that is dragging forward in a horizontal list
  • Escape esc - cancel an existing drag - regardless of whether the user is dragging with the keyboard or mouse.

Limitations of keyboard dragging

There is current limitation of keyboard dragging: the drag will cancel if the user scrolls the window. This could be worked around but for now it is the simpliest initial approach.

Carefully designed animations

With things moving a lot it would be easy for the user to become distracted by the animations or for them to get in the way. We have tweaked the various animations to ensure the right balance of guidance, performance and interactivity.

Dropping

When you drop a dragging item its movement is based on physics (thanks react-motion). This results in the drop feeling more weighted and physical.

Moving out of the way

Items that are moving out of the way of a dragging item do so with a CSS transition rather than physics. This is to maximise performance by allowing the GPU to handle the movement. The CSS animation curve has been designed to communicate getting out of the way.

How it is composed:

  1. A warm up period to mimic a natural response time
  2. A small phase to quickly move out of the way
  3. A long tail so that people can read any text that is being animated in the second half of the animation

animation curve

animation curve used when moving out of the way

Installation

# yarn
yarn add react-beautiful-dnd

# npm
npm install react-beautiful-dnd --save

API

So how do you use the library?

DragDropContext

In order to use drag and drop, you need to have the part of your React tree that you want to be able to use drag and drop in wrapped in a DragDropContext. It is advised to just wrap your entire application in a DragDropContext. Having nested DragDropContext's is not supported. You will be able to achieve your desired conditional dragging and dropping using the props of Droppable and Draggable. You can think of DragDropContext as having a similar purpose to the react-redux Provider component

Prop type information

type Hooks = {|
  onDragStart?: (initial: DragStart) => void,
  onDragEnd: (result: DropResult) => void,
|}

type Props = Hooks & {|
  children?: ReactElement,
|}

Basic usage

import { DragDropContext } from 'react-beautiful-dnd';

class App extends React.Component {
  onDragStart = () => {
    /*...*/
  };
  onDragEnd = () => {
    /*...*/
  };

  render() {
    return (
      <DragDropContext
        onDragStart={this.onDragStart}
        onDragEnd={this.onDragEnd}
      >
        <div>Hello world</div>
      </DragDropContext>
    );
  }
}

Hooks

These are top level application events that you can use to perform your own state updates.

onDragStart (optional)

This function will get notified when a drag starts. You are provided with the following details:

initial: DragStart

  • initial.draggableId: the id of the Draggable that is now dragging
  • initial.type: the type of the Draggable that is now dragging
  • initial.source: the location (droppableId and index) of where the dragging item has started within a Droppable.

This function is optional and therefore does not need to be provided. It is highly recommended that you use this function to block updates to all Draggable and Droppable components during a drag. (See Best hooks practices)

Type information

onDragStart?: (initial: DragStart) => void

// supporting types
type DragStart = {|
  draggableId: DraggableId,
  type: TypeId,
  source: DraggableLocation,
|}

type DraggableLocation = {|
  droppableId: DroppableId,
  // the position of the draggable within a droppable
  index: number
|};
type Id = string;
type DraggableId = Id;
type DroppableId = Id;
type TypeId = Id;

onDragEnd (required)

This function is extremely important and has an critical role to play in the application lifecycle. This function must result in the synchronous reordering of a list of Draggables

It is provided with all the information about a drag:

result: DropResult

  • result.draggableId: the id of the Draggable that was dragging.
  • result.type: the type of the Draggable that was dragging.
  • result.source: the location that the Draggable started in.
  • result.destination: the location that the Draggable finished in. The destination will be null if the user dropped into no position (such as outside any list) or if they dropped the Draggable back into the same position that it started in.

Synchronous reordering

Because this library does not control your state, it is up to you to synchronously reorder your lists based on the result.

Here is what you need to do:

  • if the destination is null: all done!
  • if source.droppableId equals destination.droppableId you need to remove the item from your list and insert it at the correct position.
  • if source.droppableId does not equal destination.droppable you need to the Draggable from the source.droppableId list and add it into the correct position of the destination.droppableId list.

Type information

onDragEnd: (result: DropResult) => void

// supporting types
type DropResult = {|
  draggableId: DraggableId,
  type: TypeId,
  source: DraggableLocation,
  // may not have any destination (drag to nowhere)
  destination: ?DraggableLocation
|}

type Id = string;
type DroppableId = Id;
type DraggableId = Id;
type TypeId = Id;
type DraggableLocation = {|
  droppableId: DroppableId,
  // the position of the droppable within a droppable
  index: number
|};

Best practices for hooks

Block updates during a drag

It is highly recommended that while a user is dragging that you block any state updates that might impact the amount of Draggables and Droppables, or their dimensions. Please listen to onDragStart and block updates to the Draggables and Droppables until you receive at onDragEnd.

When the user starts dragging we take a snapshot of all of the dimensions of the applicable Draggable and Droppable nodes. If these change during a drag we will not know about it.

Here are a few poor user experiences that can occur if you change things during a drag:

  • If you increase the amount of nodes the library will not know about them and they will not be moved when the user would expect them to be.
  • If you decrease the amount of nodes then there might be gaps and unexpected movements in your lists.
  • If you change the dimensions of any node, it can cause the changed node as well as others to move at incorrect times.
  • If you remove the node that the user is dragging the drag will instantly end
  • If you change the dimension of the dragging node then other things will not move out of the way at the correct time.

onDragStart and onDragEnd pairing

We try very hard to ensure that each onDragStart event is paired with a single onDragEnd event. However, there maybe a rouge situation where this is not the case. If that occurs - it is a bug. Currently there is no mechanism to tell the library to cancel a current drag externally.

Style

During a drag it is recommended that you add two styles to the body:

  1. user-select: none; and
  2. cursor: grab; (or whatever cursor you want to use while dragging)

user-select: none; prevents the user drag from selecting text on the page as they drag.

cursor: [your desired cursor]; is needed because we apply pointer-events: none; to the dragging item. This prevents you setting your own cursor style on the Draggable directly based on snapshot.isDragging (see Draggable).

Dynamic hooks

Your hook functions will only be captured once at start up. Please do not change the function after that. If there is a valid use case for this then dynamic hooks could be supported. However, at this time it is not.

Droppable

Droppable components can be dropped on by a Draggable. They also contain Draggables. A Draggable must be contained within a Droppable.

import { Droppable } from 'react-beautiful-dnd';

<Droppable droppableId="droppable-1" type="PERSON">
  {(provided, snapshot) => (
    <div
      ref={provided.innerRef}
      style={{ backgroundColor: snapshot.isDraggingOver ? 'blue' : 'grey' }}
    >
      I am a droppable!
    </div>
  )}
</Droppable>;

Props

  • droppableId: A required DroppableId(string) that uniquely identifies the droppable for the application. Please do not change this prop - especially during a drag.
  • type: An optional TypeId(string) that can be used to simply accept a class of Draggable. For example, if you use the type PERSON then it will only allow Draggables of type PERSON to be dropped on itself. Draggables of type TASK would not be able to be dropped on a Droppable with type PERSON. If no type is provided, it will be set to 'DEFAULT'. Currently the type of the Draggables within a Droppable must be the same. This restriction might be loosened in the future if there is a valid use case.
  • isDropDisabled: An optional flag to control whether or not dropping is currently allowed on the Droppable. You can use this to implement your own conditional dropping logic. It will default to false.

Children function

The React children of a Droppable must be a function that returns a ReactElement.

<Droppable droppableId="droppable-1">
  {(provided, snapshot) => ({
    /*...*/
  })}
</Droppable>;

The function is provided with two arguments:

1. provided: (Provided)

type Provided = {|
  innerRef: (HTMLElement) => void,
|}

In order for the droppable to function correctly, you must bind the provided.innerRef to the highest possible DOM node in the ReactElement. We do this in order to avoid needing to use ReactDOM to look up your DOM node.

<Droppable droppableId="droppable-1">
  {(provided, snapshot) => <div ref={provided.innerRef}>Good to go</div>}
</Droppable>;

2. snapshot: (StateSnapshot)

type StateSnapshot = {|
  isDraggingOver: boolean,
|};

The children function is also provided with a small amount of state relating to the current drag state. This can be optionally used to enhance your component. A common use case is changing the appearance of a Droppable while it is being dragged over.

<Droppable droppableId="droppable-1">
  {(provided, snapshot) => (
    <div
      ref={provided.innerRef}
      style={{ backgroundColor: snapshot.isDraggingOver ? 'blue' : 'grey' }}
    >
      I am a droppable!
    </div>
  )}
</Droppable>;

Conditionally dropping

Keep in mind that this is not supported at this time. In this current initial version we only support reordering within a single list.

  • Droppables can only be dropped on by Draggables who share the same type. This is a simple way of allowing conditional dropping. If you do not provide a type for the Droppable then it will only accept Draggables which also have the default type. Draggables and Droppables both will have their types set to 'DEFAULT' when none is provided. There is currently no way to set multiple types, or a type wildcard that will accept Draggables of multiple any types. This could be added if there is a valid use case.
  • Using the isDropDisabled prop you can conditionally allow dropping. This allows you to do arbitrarily complex conditional transitions. This will only be considered if the type of the Droppable matches the type of the currently dragging Draggable.
  • You can disable dropping on a Droppable altogether by always setting isDropDisabled to false. You can do this to create a list that is never able to be dropped on, but contains Draggables.
  • Technically you do not need to use type and do all of your conditional drop logic with the isDropDisabled function. The type parameter is a convenient shortcut for a common use case.

Scroll containers

This library supports dragging within scroll containers (DOM elements that have overflow: auto; or overflow: scroll;). The only supported use cases are:

  1. The Droppable can itself be a scroll container with no scrollable parents
  2. The Droppable has one scrollable parent

Auto scrolling is not provided

Currently auto scrolling of scroll containers is not part of this library. Auto scrolling is where the container automatically scrolls to make room for the dragging item as you drag near the edge of a scroll container. You are welcome to build your own auto scrolling list, or if you would you really like it as part of this library we could provide a auto scrolling Droppable.

Users will be able to scroll a scroll container while dragging by using their trackpad or mouse wheel.

Keyboard dragging limitation

Getting keyboard dragging to work with scroll containers is quite difficult. Currently there is a limitation: you cannot drag with a keyboard beyond the visible edge of a scroll container. This limitation could be removed if we introduced auto scrolling.

Draggable

Draggable components can be dragged around and dropped onto Droppables. A Draggable must always be contained within a Droppable. It is possible to reorder a Draggable within its home Droppable or move to another Droppable. It is possible because a Droppable is free to control what it allows to be dropped on it.

Note: moving between Droppables is currently not supported in the initial version.

import { Draggable } from 'react-beautiful-dnd';

<Draggable draggableId="draggable-1" type="PERSON">
  {(provided, snapshot) => (
    <div>
      <div
        ref={provided.innerRef}
        style={provided.draggableStyle}
        {...provided.dragHandleProps}
      >
        <h4>My draggable</h4>
      </div>
      {provided.placeholder}
    </div>
  )}
</Draggable>;

Note: when the library moves to React 16 this will be cleaned up a little bit as we will be able to return the placeholder as a sibling to your child function without you needing to create a wrapping element

Props

  • draggableId: A required DraggableId(string) that uniquely identifies the Draggable for the application. Please do not change this prop - especially during a drag.
  • type: An optional type (TypeId(string)) of the Draggable. This is used to control what Droppables the Draggable is permitted to drop on. Draggables can only drop on Droppables that share the same type. If no type is provided, it will be set to 'DEFAULT'. Currently the type of a Draggable must be the same as its container Droppable. This restriction might be loosened in the future if there is a valid use case.
  • isDragDisabled: An optional flag to control whether or not the Draggable is permitted to drag. You can use this to implement your own conditional drag logic. It will default to false.

Children function

The React children of a Draggable must be a function that returns a ReactElement.

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => (
    <div>
      <div
        ref={provided.innerRef}
        style={provided.draggableStyle}
        {...provided.dragHandleProps}
      >
        Drag me!
      </div>
      {provided.placeholder}
    </div>
  )}
</Draggable>;

The function is provided with two arguments:

1. provided: (Provided)

type Provided = {|
  innerRef: (HTMLElement) => void,
  draggableStyle: ?DraggableStyle,
  dragHandleProps: ?DragHandleProvided,
  placeholder: ?ReactElement,
|}

Everything within the provided object must be applied for the Draggable to function correctly.

  • provided.innerRef (innerRef: (HTMLElement) => void): In order for the Droppable to function correctly, you must bind the innerRef function to the ReactElement that you want to be considered the Draggable node. We do this in order to avoid needing to use ReactDOM to look up your DOM node.
<Draggable draggableId="draggable-1">
  {(provided, snapshot) => <div ref={provided.innerRef}>Drag me!</div>}
</Draggable>;

Type information

innerRef: (HTMLElement) => void
  • provided.draggableStyle (?DraggableStyle): This is an Object or null that contains an a number of styles that needs to be applied to the Draggable. This needs to be applied to the same node that you apply provided.innerRef to. This controls the movement of the draggable when it is dragging and not dragging. You are welcome to add your own styles to this object – but please do not remove or replace any of the properties.

Ownership

It is a contract of this library that it owns the positioning logic of the dragging element. This includes properties such as top, right, bottom, left and transform. The library may change how it positions things and what properties it uses without performing a major version bump. It is also recommended that you do not apply your own transition property to the dragging element.

Warning: position: fixed

react-beautiful-dnd uses position: fixed to position the dragging element. This is quite robust and allows for you to have position: relative | absolute | fixed parents. However, unfortunately position:fixed is impacted by transform (such as transform: rotate(10deg);). This means that if you have a transform: * on one of the parents of a Draggable then the positioning logic will be incorrect while dragging. Lame! For most consumers this will not be an issue. We may look into creating a portal solution where we attach the dragging element to the body rather than leave it in place. However, leaving it in place is a really nice experience for everyone. For now we will leave it as is, but feel free to raise an issue if you this is important to you.

Usage of draggableStyle

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => (
    <div>
      <div ref={provided.innerRef} style={provided.draggableStyle}>
        Drag me!
      </div>
    </div>
  )}
</Draggable>;

Extending with your own styles

<Draggable draggable="draggable-1">
  {(provided, snapshot) => {
    const style = {
      ...provided.draggableStyle,
      backgroundColor: snapshot.isDragging ? 'blue' : 'white',
      fontSize: 18,
    };
    return (
      <div>
        <div ref={provided.innerRef} style={style}>
          Drag me!
        </div>
      </div>
    );
  }}
</Draggable>;

Type information

type DraggableStyle = DraggingStyle | NotDraggingStyle;

type DraggingStyle = {|
  pointerEvents: 'none',
  position: 'fixed',
  width: number,
  height: number,
  boxSizing: 'border-box',
  top: number,
  left: number,
  margin: 0,
  transform: ?string,
  zIndex: ZIndex,
|}

type NotDraggingStyle = {|
  transition: ?string,
  transform: ?string,
  pointerEvents: 'none' | 'auto',
|};
  • provided.placeholder (?ReactElement) The Draggable element has position: fixed applied to it while it is dragging. The role of the placeholder is to sit in the place that the Draggable was during a drag. It is needed to stop the Droppable list from collapsing when you drag. It is advised to render it as a sibling to the Draggable node. When the library moves to React 16 the placeholder will be removed from api.
<Draggable draggableId="draggable-1">
  {(provided, snapshot) => (
    <div>
      <div ref={provided.innerRef} style={provided.draggableStyle}>
        Drag me!
      </div>
      {/* Always render me - I will be null if not required */}
      {provided.placeholder}
    </div>
  )}
</Draggable>;
  • provided.dragHandleProps (?DragHandleProps) every Draggable has a drag handle. This is what is used to drag the whole Draggable. Often this will be the same node as the Draggable, but sometimes it can be a child of the Draggable. DragHandleProps need to be applied to the node that you want to be the drag handle. This is a number of props that need to be applied to the Draggable node. The simpliest approach is to spread the props onto the draggable node ({...provided.dragHandleProps}). However, you are also welcome to monkey patch these props if you also need to respond to them. DragHandleProps will be null when isDragDisabled is set to true.

Type information

type DragHandleProps = {|
  onMouseDown: (event: MouseEvent) => void,
  onKeyDown: (event: KeyboardEvent) => void,
  onClick: (event: MouseEvent) => void,
  tabIndex: number,
  'aria-grabbed': boolean,
  draggable: boolean,
  onDragStart: () => void,
  onDrop: () => void,
|};

Standard example

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => (
    <div>
      <div
        ref={provided.innerRef}
        style={provided.draggableStyle}
        {...provided.dragHandleProps}
      >
        Drag me!
      </div>
      {provided.placeholder}
    </div>
  )}
</Draggable>;

Custom drag handle

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => (
    <div>
      <div ref={provided.innerRef} style={provided.draggableStyle}>
        <h2>Hello there</h2>
        <div {...provided.dragHandleProps}>Drag handle</div>
      </div>
      {provided.placeholder}
    </div>
  )}
</Draggable>;

Monkey patching

If you want to also use one of the props in DragHandleProps

const myOnClick = event => console.log('clicked on', event.target);

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => {
    const onClick = (() => {
      // dragHandleProps might be null
      if (!provided.dragHandleProps) {
        return myOnClick;
      }

      // creating a new onClick function that calls my onClick
      // event as well as the provided one.
      return event => {
        provided.dragHandleProps.onClick(event);
        // You may want to check if event.defaultPrevented
        // is true and optionally fire your handler
        myOnClick(event);
      };
    })();

    return (
      <div>
        <div
          ref={provided.innerRef}
          style={provided.draggableStyle}
          {...provided.dragHandleProps}
          onClick={onClick}
        >
          Drag me!
        </div>
        {provided.placeholder}
      </div>
    );
  }}
</Draggable>;

2. snapshot: (StateSnapshot)

type StateSnapshot = {|
  isDragging: boolean,
|};

The children function is also provided with a small amount of state relating to the current drag state. This can be optionally used to enhance your component. A common use case is changing the appearance of a Draggable while it is being dragged. Note: if you want to change the cursor to something like grab you will need to add the style to the body. (See DragDropContext > style above)

<Draggable draggableId="draggable-1">
  {(provided, snapshot) => {
    const style = {
      ...provided.draggableStyle,
      backgroundColor: snapshot.isDragging ? 'blue' : 'grey',
    };

    return (
      <div>
        <div
          ref={provided.innerRef}
          style={style}
          {...provided.dragHandleProps}
        >
          Drag me!
        </div>
        {provided.placeholder}
      </div>
    );
  }}
</Draggable>;

Engineering health

Typed

This codebase is typed with flowtype to promote greater internal consistency and more resilient code.

Tested

This code base employs a number of different testing strategies including unit, performance and integration tests. Testing various aspects of the system helps to promote its quality and stability.

While code coverage is not a guarantee of code health, it is a good indicator. This code base currently sits at ~95% coverage.

Performance

This codebase is designed to be extremely performant - it is part of its DNA. It builds on prior investigations into React performance that you can read about here and here. It is designed to perform the minimum number of renders required for each task.

Highlights

  • using connected-components with memoization to ensure the only components that render are the ones that need to - thanks react-redux, reselect and memoize-one
  • all movements are throttled with a requestAnimationFrame - thanks raf-schd
  • memoization is used all over the place - thanks memoize-one
  • conditionally disabling pointer-events on Draggables while dragging to prevent the browser needing to do redundant work - you can read more about the technique here
  • Non primary animations are done on the GPU

minimal-browser-paints
minimal-react-updates

GitHub