react-spring/targets/web/src/applyAnimatedValues.ts

import { Lookup } from '@react-spring/types'

const isCustomPropRE = /^--/

type Value = string | number | boolean | null

function dangerousStyleValue(name: string, value: Value) {
  if (value == null || typeof value === 'boolean' || value === '') return ''
  if (
    typeof value === 'number' &&
    value !== 0 &&
    !isCustomPropRE.test(name) &&
    !(isUnitlessNumber.hasOwnProperty(name) && isUnitlessNumber[name])
  )
    return value + 'px'
  // Presumes implicit 'px' suffix for unitless numbers
  return ('' + value).trim()
}

const attributeCache: Lookup<string> = {}

type Instance = HTMLDivElement & { style?: Lookup }

export function applyAnimatedValues(instance: Instance, props: Lookup) {
  if (!instance.nodeType || !instance.setAttribute) {
    return false
  }

  const isFilterElement =
    instance.nodeName === 'filter' ||
    (instance.parentNode && instance.parentNode.nodeName === 'filter')

  const {
    className,
    style,
    children,
    scrollTop,
    scrollLeft,
    viewBox,
    ...attributes
  } = props!

  const values = Object.values(attributes)
  const names = Object.keys(attributes).map(name =>
    isFilterElement || instance.hasAttribute(name)
      ? name
      : attributeCache[name] ||
        (attributeCache[name] = name.replace(
          /([A-Z])/g,
          // Attributes are written in dash case
          n => '-' + n.toLowerCase()
        ))
  )

  if (children !== void 0) {
    instance.textContent = children
  }

  // Apply CSS styles
  for (const name in style) {
    if (style.hasOwnProperty(name)) {
      const value = dangerousStyleValue(name, style[name])
      if (isCustomPropRE.test(name)) {
        instance.style.setProperty(name, value)
      } else {
        instance.style[name] = value
      }
    }
  }

  // Apply DOM attributes
  names.forEach((name, i) => {
    instance.setAttribute(name, values[i])
  })

  if (className !== void 0) {
    instance.className = className
  }
  if (scrollTop !== void 0) {
    instance.scrollTop = scrollTop
  }
  if (scrollLeft !== void 0) {
    instance.scrollLeft = scrollLeft
  }
  if (viewBox !== void 0) {
    instance.setAttribute('viewBox', viewBox)
  }
}

let isUnitlessNumber: { [key: string]: true } = {
  animationIterationCount: true,
  borderImageOutset: true,
  borderImageSlice: true,
  borderImageWidth: true,
  boxFlex: true,
  boxFlexGroup: true,
  boxOrdinalGroup: true,
  columnCount: true,
  columns: true,
  flex: true,
  flexGrow: true,
  flexPositive: true,
  flexShrink: true,
  flexNegative: true,
  flexOrder: true,
  gridRow: true,
  gridRowEnd: true,
  gridRowSpan: true,
  gridRowStart: true,
  gridColumn: true,
  gridColumnEnd: true,
  gridColumnSpan: true,
  gridColumnStart: true,
  fontWeight: true,
  lineClamp: true,
  lineHeight: true,
  opacity: true,
  order: true,
  orphans: true,
  tabSize: true,
  widows: true,
  zIndex: true,
  zoom: true,
  // SVG-related properties
  fillOpacity: true,
  floodOpacity: true,
  stopOpacity: true,
  strokeDasharray: true,
  strokeDashoffset: true,
  strokeMiterlimit: true,
  strokeOpacity: true,
  strokeWidth: true,
}

const prefixKey = (prefix: string, key: string) =>
  prefix + key.charAt(0).toUpperCase() + key.substring(1)
const prefixes = ['Webkit', 'Ms', 'Moz', 'O']

isUnitlessNumber = Object.keys(isUnitlessNumber).reduce((acc, prop) => {
  prefixes.forEach(prefix => (acc[prefixKey(prefix, prop)] = acc[prop]))
  return acc
}, isUnitlessNumber)