vue中4个自定义指令讲解及实例用法

Vue.directive('drag', {
  inserted(el) {
    let header = el.querySelector('.dialog_header')
    header.style.cssText += ';cursor:move;'
    header.onmousedown = function (e) {
      //获取当前可视区域宽、高
      let clientWidth = document.documentElement.clientWidth
      let clientHeight = document.documentElement.clientHeight
 
      //获取自身宽高
      let elWidth = el.getBoundingClientRect().width
      let elHeight = el.getBoundingClientRect().height
 
      //获取当前距离可视区域的top、left
      let elTop = el.getBoundingClientRect().top
      let elLeft = el.getBoundingClientRect().left
 
      //获取点击时候的坐标
      let startX = e.pageX
      let startY = e.pageY
 
      document.onmousemove = function (e) {
        //元素偏移量 = 鼠标滑动后的坐标 - 鼠标初始点击元素时的坐标 + 初始点击时元素距离可视区域的top、left
        let moveX = e.pageX - startX + elLeft
        let moveY = e.pageY - startY + elTop
 
        //将可视区域作为边界，限制在可视区域里面拖拽
        if ((moveX + elWidth) > clientWidth || moveX < 0 || (moveY + elHeight) > clientHeight || moveY < 0) {
          return
        }
 
        el.style.cssText += 'top:' + moveY + 'px;left:' + moveX + 'px;'
      }
      document.onmouseup = function () {
        document.onmousemove = null
        document.onmouseup = null
      }
    }
  }
})

Vue.directive('wordlimit',{
  bind(el,binding){
    console.log('bind');
    let { value } = binding
    Vue.nextTick(() =>{
      //找到输入框是textarea框还是input框
      let current = 0
      let arr = Array.prototype.slice.call(el.children)
      for (let i = 0; i < arr.length; i++) {
        if(arr[i].tagName=='TEXTAREA' || arr[i].tagName=='INPUT'){
          current = i
        }
      }
   
      //更新当前输入框的字节数
      el.children[el.children.length-1].innerHTML = el.children[current].value.replace(/[^\x00-\xff]/g,'**').length +'/'+value//eslint-disable-line
    })
  },
  update(el,binding){
    console.log('update');
    let { value } = binding
    Vue.nextTick(() =>{
      //找到输入框是textarea框还是input框
      let current = 0
      let arr = Array.prototype.slice.call(el.children)
      for (let i = 0; i < arr.length; i++) {
        if(arr[i].tagName=='TEXTAREA' || arr[i].tagName=='INPUT'){
          current = i
        }
      }
   
      //更新当前输入框的字节数
      el.children[el.children.length-1].innerHTML = el.children[current].value.replace(/[^\x00-\xff]/g,'**').length +'/'+value//eslint-disable-line
    })
  },
  inserted(el,binding){
    console.log('inserted');
    let { value } = binding
 
    //找到输入框是textarea框还是input框
    let current = 0
    let arr = Array.prototype.slice.call(el.children)
    for (let i = 0; i < arr.length; i++) {
      if(arr[i].tagName=='TEXTAREA' || arr[i].tagName=='INPUT'){
        current = i
      }
    }
 
    //创建包裹字数限制的元素，并定位布局在textarea和input框上
    let div = document.createElement('div')
    if(el.children[current].tagName=='TEXTAREA'){//是textarea，定位在右下角
      div.style = 'color:#909399;position:absolute;font-size:12px;bottom:5px;right:10px;'
    }else{
      let styStr = ''
      if(!el.classList.contains('is-disabled')){//input框不是置灰的状态则添加背景颜色
        styStr = 'background:#fff;'
      }
      div.style = 'color:#909399;position:absolute;font-size:12px;bottom:2px;right:10px;line-height:28px;height:28px;'+styStr
    }
 
    div.innerHTML = '0/'+ value
    el.appendChild(div)
    el.children[current].style.paddingRight = '60px'
 
    el.oninput = () =>{
      let val = el.children[current].value
      val = val.replace(/[^\x00-\xff]/g,'**') //eslint-disable-line
      // 字数限制的盒子插入到el后是最后一个元素
      el.children[el.children.length-1].innerHTML = val.length + '/' + value
      if(val.length>value){
        let cnLen = 0 //一个字节的字数
        let enLen = 0 //两个字节的字数
 
        if(val.match(/[^**]/g) && val.match(/[^**]/g).length){
          enLen = val.match(/[^**]/g).length // 计算一个字节的字数
 
          //一个字节两个字节都有的情况
          if((value - val.match(/[^**]/g).length)>0){
            cnLen = Math.floor((value - val.match(/[^**]/g).length)/2)
          }else{
            cnLen = 0
          }
        }else{ //全部两个字节的情况
          enLen = 0
          cnLen = Math.floor(value/2)
        }
 
        if(enLen>value){
          enLen = value
        }
 
        //超过限定字节数则截取
        el.children[current].value = el.children[current].value.substr(0,enLen+cnLen)
 
        //更新当前输入框的字节数
        el.children[el.children.length-1].innerHTML = el.children[current].value.replace(/[^\x00-\xff]/g,'**').length +'/'+value//eslint-disable-line
 
      }
    }
 
  },
})

<el-input type="textarea" rows="3" v-wordlimit="20" v-model="value"></el-input>

Vue.directive('anchor',{
  inserted(el,binding){
    let { value } = binding
    let timer = null
    el.addEventListener('click',function(){
      // 当前元素距离可视区域顶部的距离
      let currentTop = el.getBoundingClientRect().top
      animateScroll(currentTop)
    },false)
     
    function animateScroll(currentTop){
      if(timer){
        clearInterval(timer)
      }
      let c = 9
      timer = setInterval(() =>{
        if(c==0){
          clearInterval(timer)
        }
        c--
        window.scrollBy(0,(currentTop-value)/10)
      },16.7)
    }
 
  }
})

<div class="box" v-anchor="20" style="color:red;">是的</div>

Vue.directive('hasRole',{
  inserted(el,binding){
    let { value } = binding
    let roles = JSON.parse(sessionStorage.getItem('userInfo')).roleIds
 
    if(value && value instanceof Array && value.length>0){
 
      let hasPermission = value.includes(roles)
 
      if(!hasPermission){
        el.parentNode && el.parentNode.removeChild(el)
      }
    }else{
      throw new Error(`请检查指令绑定的表达式，正确格式例如 v-hasRole="['admin','reviewer']"`)
    }
  }
})