ShouBo/web/src/utils.js

function mapTags(tag) {
  let ret = ''
  switch (tag) {
  case 'A':
    ret = 'Link'
    break
  case 'BUTTON':
    ret = 'Button'
    break
  case 'IMG':
    ret = 'Image'
    break
  case 'INPUT':
    ret = 'Textbox'
    break
  case 'TEXTAREA':
    ret = 'Textbox'
    break
  default:
    ret = ''
    // ret = 'Text'
    break
  }
  return ret
}

function extractTextForFocus(e) {
  let meaningfulNode = e.target

  // 如果天然能focus，但没有被加上tabindex属性，比如focus到了第三方组件内部的可focus元素，直接返回。
  if (
    ['A', 'AREA', 'BUTTON', 'INPUT', 'SELECT', 'IFRAME'].includes(meaningfulNode.tagName) &&
    !meaningfulNode.getAttribute('tabindex')
  ) {
    return
  }

  while (!meaningfulNode.getAttribute || !meaningfulNode.getAttribute('tabindex')) {
    meaningfulNode = meaningfulNode.parentNode
    if (!meaningfulNode) {
      return
    }
  }

  // 约定：tabindex属性值为-1的元素只用于在点击有data-aria-xxx-area attribute的区域包裹元素的子孙元素时，避免focus到区域包裹元素。
  if (meaningfulNode.getAttribute('tabindex') === '-1') {
    return
  }

  let elemType = ''
  const ariaLabel = meaningfulNode.getAttribute('aria-label')
  if (ariaLabel !== null) {
    elemType = ariaLabel
  } else {
    elemType = mapTags(meaningfulNode.tagName)
  }

  let elemDisc = ''
  const ariaDescription = meaningfulNode.getAttribute('aria-description')
  if (ariaDescription !== null) {
    elemDisc = ariaDescription
  } else {
    elemDisc = meaningfulNode.innerText
  }

  return {
    elemType,
    elemDisc,
    ariaNode: meaningfulNode,
  }
}

let lastMeaningfulNode = null
function extractTextForMouseOver(e) {
  let meaningfulNode = e.target

  while (!meaningfulNode.getAttribute || !meaningfulNode.getAttribute('tabindex')) {
    meaningfulNode = meaningfulNode.parentNode
    if (!meaningfulNode) {
      lastMeaningfulNode = null
      return
    }
  }

  if (meaningfulNode.getAttribute('tabindex') === '-1') {
    lastMeaningfulNode = null
    return
  }

  // mouseover事件冒泡到有data-aria-xxx-area attribute的区域包裹元素时，不应该提取该区域包裹元素的无障碍辅助信息。
  if (
    meaningfulNode.getAttribute('data-aria-navigation-area') !== null ||
    meaningfulNode.getAttribute('data-aria-viewport-area') !== null ||
    meaningfulNode.getAttribute('data-aria-interaction-area') !== null
  ) {
    lastMeaningfulNode = null
    return
  }

  // 如果只是在需要朗读的子元素之间进进出出，第一次需要朗读，以后就不需要朗读了。
  let relatedMeaningfulNode = e.relatedTarget
  while (relatedMeaningfulNode && (!relatedMeaningfulNode.getAttribute || !relatedMeaningfulNode.getAttribute('tabindex'))) {
    relatedMeaningfulNode = relatedMeaningfulNode.parentNode
  }
  if (relatedMeaningfulNode === meaningfulNode && lastMeaningfulNode === meaningfulNode) {
    return
  }
  
  lastMeaningfulNode = meaningfulNode

  let elemType = ''
  const ariaLabel = meaningfulNode.getAttribute('aria-label')
  if (ariaLabel !== null) {
    elemType = ariaLabel
  } else {
    elemType = mapTags(meaningfulNode.tagName)
  }

  let elemDisc = ''
  const ariaDescription = meaningfulNode.getAttribute('aria-description')
  if (ariaDescription !== null) {
    elemDisc = ariaDescription
  } else {
    elemDisc = meaningfulNode.innerText
  }

  return {
    elemType,
    elemDisc,
    ariaNode: meaningfulNode,
  }
}

function isObject(p) {
  return Object.prototype.toString.call(p) === '[object Object]'
}

// 判断两个对象内容是否相同
function isSameObject(object1, object2) {
  const keys1 = Object.keys(object1)
  const keys2 = Object.keys(object2)

  if (keys1.length !== keys2.length) {
    return false
  }

  for (let index = 0; index < keys1.length; index++) {
    const val1 = object1[keys1[index]]
    const val2 = object2[keys2[index]]
    const areObjects = isObject(val1) && isObject(val2)
    if (
      (areObjects && !isSameObject(val1, val2)) ||
      (!areObjects && (val1 !== val2))
    ) {
      return false
    }
  }
  return true
}

function getAndFocusNextNodeWithCustomAttribute(attriName) {
  const startNode = (document.activeElement || document.body)

  const treeWalker = document.createTreeWalker(document.body, NodeFilter.SHOW_ELEMENT)
  treeWalker.currentNode = startNode

  let targetNode = null

  // eslint-disable-next-line
  while(true) {
    const nextNode = treeWalker.nextNode()
    if (!nextNode) {
      console.log('往下没找到')
      break
    }
    if (nextNode.dataset[attriName] !== undefined) {
      console.log('往下找到了')
      targetNode = nextNode
      break
    }
  }

  if (!targetNode && (startNode !== document.body)) {
    treeWalker.currentNode = document.body
    // eslint-disable-next-line
    while(true) {
      const nextNode = treeWalker.nextNode()
      if (!nextNode) {
        console.log('往上也没找到')
        break
      }
      if (nextNode.dataset[attriName] !== undefined) {
        console.log('往上找到了')
        targetNode = nextNode
        break
      }
    }
  }

  if (targetNode) {
    // 如果重复选中某一区域，需要重新触发focus，所以先blur一下
    if (document.activeElement === targetNode) {
      targetNode.blur()
    }
    targetNode.focus()

    // 如果无法focus，就强行focus
    if (document.activeElement !== targetNode) {
      targetNode.setAttribute('tabindex', '0')
      targetNode.focus()
    }
  }

  return targetNode
}

function __focusNextFocusableNode(treeWalker) {
  // eslint-disable-next-line
  while(true) {
    const nextNode = treeWalker.nextNode()
    if (!nextNode) {
      return false
    }
    if (nextNode.focus) {
      nextNode.focus()
      if (document.activeElement === nextNode && nextNode.tabIndex !== -1) {
        return true
      }
    }
  }
}

function iterateOnFocusableNode(startNode, focusedNodeHandler) {
  const treeWalker = document.createTreeWalker(document.body, NodeFilter.SHOW_ELEMENT)
  treeWalker.currentNode = startNode
  treeWalker.currentNode.focus()
  if (document.activeElement === treeWalker.currentNode) {
    // console.log('起始节点可以focus')
  } else {
    // console.log('起始节点不可以focus，focus到下一节点。')
    const ret = __focusNextFocusableNode(treeWalker)
    if (!ret) {
      return
    }
  }

  const iterator = () => {
    focusedNodeHandler(treeWalker.currentNode).then(() => {
      const result = __focusNextFocusableNode(treeWalker)
      if (result) {
        // console.log('遍历到下一个节点！')
        iterator()
      } else {
        // console.log('遍历结束！')
      }
    }).catch((e) => {
      // console.log('遍历中止！', e)
    })
  }
  iterator()
}

/**
 * 返回一个自带消抖效果的函数，用res表示。
 *
 * fn: 需要被消抖的函数
 * delay: 消抖时长
 * isImmediateCall: 是否在一组操作中的第一次调用时立即执行fn
 * isRememberLastCall：是否在一组中最后一次调用后等delay时长再执行fn
 */
function debounce(fn, delay, isImmediateCall = false, isRememberLastCall = true) {
  console.assert(isImmediateCall || isRememberLastCall, 'isImmediateCall 和 isRememberLastCall 至少应有一个是true，否则没有意义！')
  let timer = null
  // 上次调用的时刻
  let lastCallTime = 0

  if (isImmediateCall && !isRememberLastCall) {
    return function (...args) {
      const currentTime = Date.now()
      if (currentTime - lastCallTime >= delay) {
        fn.apply(this, args)
      }
      lastCallTime = currentTime
    }
  } else if (!isImmediateCall && isRememberLastCall) {
    return function (...args) {
      if (timer) {
        clearTimeout(timer)
      }
      timer = setTimeout(() => {
        fn.apply(this, args)
      }, delay)
    }
  } else if (isImmediateCall && isRememberLastCall) {
    return function (...args) {
      const currentTime = Date.now()
      if (currentTime - lastCallTime >= delay) { // 一组操作中的第一次
        fn.apply(this, args) 
        lastCallTime = currentTime
        return
      } else { // 一组中的后续调用
        if (timer) { // 在此之前存在中间调用
          lastCallTime = currentTime
          clearTimeout(timer)
        }
        timer = setTimeout(() => {
          fn.apply(this, args)
          lastCallTime = 0
          timer = null
        }, delay)
      }
    }
  } else {
    console.error('不应该执行到这里！')
  }
}

class DebounceScheduler {
  constructor(fn, delay, context, isImmediateCall = false) {
    this.job = fn
    this.delay = delay
    this.context = context
    this.timer = null
    this.lastCallTime = 0
    this.isImmediateCall = isImmediateCall
  }
  planToDo(...args) {
    if (!this.isImmediateCall) {
      if (this.timer) {
        clearTimeout(this.timer)
        this.timer = null
      }
      this.timer = setTimeout(() => {
        this.job.apply(this.context, args)
      }, this.delay)
    } else {
      const currentTime = Date.now()
      if (currentTime - this.lastCallTime >= this.delay) { // 一组操作中的第一次
        this.job.apply(this.context, args) 
        this.lastCallTime = currentTime
        return
      } else { // 一组中的后续调用
        if (this.timer) { // 在此之前存在中间调用
          this.lastCallTime = currentTime
          clearTimeout(this.timer)
          this.timer = null
        }
        this.timer = setTimeout(() => {
          this.job.apply(this.context, args)
          this.lastCallTime = 0
          this.timer = null
        }, this.delay)
      }
    }
  }
  cancel() {
    if (this.timer) {
      clearTimeout(this.timer)
      this.timer = null
    }
  }
}

export default {
  mapTags,
  extractTextForFocus,
  extractTextForMouseOver,
  isSameObject,
  getAndFocusNextNodeWithCustomAttribute,
  iterateOnFocusableNode,
  debounce,
  DebounceScheduler,
}