---
id: example-drag
title: Drag
sidebar_label: Drag
---

> **Note**
>
> This example only works with a real browser (not with jsdom, as it does not
> support `getBoundingClientRect`).

# Usage

```js
await drag(slider, {
  delta: {x: -100, y: 0},
})
```

# Capture

![slider-testing-lib](https://user-images.githubusercontent.com/880132/80156530-0efc8f00-85bc-11ea-902c-c4e0f11a2579.gif)

# Code

```js
import {fireEvent} from '@testing-library/dom'

// https://stackoverflow.com/a/53946549/1179377
function isElement(obj) {
  if (typeof obj !== 'object') {
    return false
  }
  let prototypeStr, prototype
  do {
    prototype = Object.getPrototypeOf(obj)
    // to work in iframe
    prototypeStr = Object.prototype.toString.call(prototype)
    // '[object Document]' is used to detect document
    if (
      prototypeStr === '[object Element]' ||
      prototypeStr === '[object Document]'
    ) {
      return true
    }
    obj = prototype
    // null is the terminal of object
  } while (prototype !== null)
  return false
}

function getElementClientCenter(element) {
  const {left, top, width, height} = element.getBoundingClientRect()
  return {
    x: left + width / 2,
    y: top + height / 2,
  }
}

const getCoords = charlie =>
  isElement(charlie) ? getElementClientCenter(charlie) : charlie

const sleep = ms =>
  new Promise(resolve => {
    setTimeout(resolve, ms)
  })

export default async function drag(
  element,
  {to: inTo, delta, steps = 20, duration = 500},
) {
  const from = getElementClientCenter(element)
  const to = delta
    ? {
        x: from.x + delta.x,
        y: from.y + delta.y,
      }
    : getCoords(inTo)

  const step = {
    x: (to.x - from.x) / steps,
    y: (to.y - from.y) / steps,
  }

  const current = {
    clientX: from.x,
    clientY: from.y,
  }

  fireEvent.mouseEnter(element, current)
  fireEvent.mouseOver(element, current)
  fireEvent.mouseMove(element, current)
  fireEvent.mouseDown(element, current)
  for (let i = 0; i < steps; i++) {
    current.clientX += step.x
    current.clientY += step.y
    await sleep(duration / steps)
    fireEvent.mouseMove(element, current)
  }
  fireEvent.mouseUp(element, current)
}
```