关于javascript:实现搜索高亮

<template>
<div class=”search-highlight” v-html=”contentShow”>
</div>
</template>

<script>
const PLUGIN_FLAG = ‘search-hightlight_by_mumaa’
export default {
props: {

content: {
  type: String,
  default: ''
},
keyword: {
  type: String,
  default: ''
},
highlightStyle: {
  type: String,
  default: 'background: #ffff00'
},
currentStyle: {
  type: String,
  default: 'background: #ff9632'
},
regExp: {
  type: Boolean,
  default: false
}

},
data () {

return {
  lightIndex: 0,
  matchCount: 0,
  contentShow: '',
  random: `${Math.random()}`.slice(2)
}

},
computed: {

watchString () {return [this.content, this.keyword]
},
watchStyle () {return [this.lightIndex, this.highlightStyle, this.currentStyle]
},
flag () {return `${PLUGIN_FLAG}${this.random}`
},
styleSelector () {return `style[${this.flag}]`
},

},
watch: {

watchString: {
  immediate: true,
  handler () {this.replaceKeywords()
  }
},
watchStyle: {
  immediate: true,
  handler () {this.setStyle()
  }
},
lightIndex: {
  immediate: true,
  handler () {this.$emit('current-change', this.lightIndex)
  }
},
matchCount: {
  immediate: true,
  handler () {this.$emit('match-count-change', this.matchCount)
  }
}

},
beforeDestroy () {

this.clearStyle()

},
methods: {

getTextNodeList (dom) {const nodeList = [...dom.childNodes]
  const textNodes = []
  while (nodeList.length) {const node = nodeList.shift()
    if (node.nodeType === node.TEXT_NODE) {node.wholeText && textNodes.push(node)
    } else {nodeList.unshift(...node.childNodes)
    }
  }
  return textNodes
},
getTextInfoList (textNodes) {
  let length = 0
  const textList = textNodes.map(node => {
    let startIdx = length, endIdx = length + node.wholeText.length
    length = endIdx
    return {
      text: node.wholeText,
      startIdx,
      endIdx
    }
  })
  return textList
},
getMatchList (content, keyword) {if (!this.regExp) {const characters = [...'\\[](){}?.+*^$:|'].reduce((r, c) => (r = true, r), {})
    keyword = keyword.split('').map(s => characters[s] ? `\\${s}` : s).join('[\\s\\n]*')
  }
  const reg = new RegExp(keyword, 'gmi')
  const matchList = []
  let match = reg.exec(content)
  while (match) {matchList.push(match)
    match = reg.exec(content)
  }
  return matchList
},
replaceMatchResult (textNodes, textList, matchList) {
  // 对于每一个匹配后果，可能扩散在多个标签中，找出这些标签，截取匹配片段并用 font 标签替换出
  for (let i = matchList.length - 1; i >= 0; i--) {const match = matchList[i]
    const matchStart = match.index, matchEnd = matchStart + match[0].length // 匹配后果在拼接字符串中的起止索引
    // 遍历文本信息列表，查找匹配的文本节点
    for (let textIdx = 0; textIdx < textList.length; textIdx++) {const { text, startIdx, endIdx} = textList[textIdx] // 文本内容、文本在拼接串中开始、完结索引
      if (endIdx < matchStart) continue // 匹配的文本节点还在前面
      if (startIdx >= matchEnd) break // 匹配文本节点曾经解决完了
      let textNode = textNodes[textIdx] // 这个节点中的局部或全部内容匹配到了关键词，将匹配局部截取进去进行替换
      const nodeMatchStartIdx = Math.max(0, matchStart - startIdx) // 匹配内容在文本节点内容中的开始索引
      const nodeMatchLength = Math.min(endIdx, matchEnd) - startIdx - nodeMatchStartIdx // 文本节点内容匹配关键词的长度
      if (nodeMatchStartIdx > 0) textNode = textNode.splitText(nodeMatchStartIdx) // textNode 取后半局部
      if (nodeMatchLength < textNode.wholeText.length) textNode.splitText(nodeMatchLength)
      const font = document.createElement('font')
      font.setAttribute(this.flag, i + 1)
      font.innerText = text.substr(nodeMatchStartIdx, nodeMatchLength)
      textNode.parentNode.replaceChild(font, textNode)
    }
  }
},
replaceKeywords () {
  let flag = false
  if (this.regExp) {
    try {const reg = new RegExp(this.keyword)
      if (reg.test('')) flag = 1
    } catch (err) {flag = 1}
  }
  if (flag || !this.keyword) {
    this.contentShow = this.content
    return
  }
  const div = document.createElement('div')
  div.innerHTML = this.content
  const textNodes = this.getTextNodeList(div)
  const textList = this.getTextInfoList(textNodes)
  const content = textList.map(({text}) => text).join('')
  const matchList = this.getMatchList(content, this.keyword)
  this.matchCount = matchList.length
  this.lightIndex = this.matchCount ? 1 : 0
  this.replaceMatchResult(textNodes, textList, matchList)
  this.contentShow = div.innerHTML
},
scrollTo (index) {this.$nextTick(() => {let node = this.$el.querySelector(`font[${this.flag}='${index}']`)
    if (node) {
      this.lightIndex = index
      node.scrollIntoView()}
  })
},
searchNext () {this.$nextTick(() => {
    let idx = this.lightIndex >= this.matchCount ? 1 : this.lightIndex + 1
    this.scrollTo(idx)
  })
},
searchLast () {this.$nextTick(() => {
    let idx = this.lightIndex <= 1 ? this.matchCount : this.lightIndex - 1
    this.scrollTo(idx)
  })
},
setStyle () {let style = document.head.querySelector(this.styleSelector)
  if (!style) {style = document.createElement('style')
    style.setAttribute(this.flag, 1)
  }
  style.innerText = `font[${this.flag}]{${this.highlightStyle}}font[${this.flag}='${this.lightIndex}']{${this.currentStyle}}`
  document.head.appendChild(style)
},
clearStyle () {let style = document.head.querySelector(this.styleSelector)
  style && document.head.removeChild(style)
}

}
}
</script>