创建waterMark.js文件

/**  水印添加方法  */let setWatermark = (str1, str2) => {let id = '1.23452384164.123412415'if (document.getElementById(id) !== null) {document.body.removeChild(document.getElementById(id))}let can = document.createElement('canvas')// 设置canvas画布大小// 控制水印的行数与列数  这个大小指的是单个水印大小can.width = 500can.height = 300let cans = can.getContext('2d')cans.rotate(-20 * Math.PI / 180) // 水印旋转角度cans.font = '50px Vedana'cans.fillStyle = '#666666'cans.textAlign = 'center'cans.textBaseline = 'Middle'cans.fillText(str1, can.width / 2, can.height) // 水印在画布的位置x，y轴cans.fillText(str2, can.width / 2, can.height + 22)let div = document.createElement('div')div.id = iddiv.style.pointerEvents = 'none'div.style.top = '40px'div.style.left = '0px'div.style.opacity = '0.2'div.style.position = 'fixed'div.style.zIndex = '100000'div.style.width = document.documentElement.clientWidth + 'px'div.style.height = document.documentElement.clientHeight + 'px'div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat'document.body.appendChild(div)return id
}// 添加水印方法
export const setWaterMark = (str1, str2) => {let id = setWatermark(str1, str2)if (document.getElementById(id) === null) {id = setWatermark(str1, str2)}
}// 移除水印方法
export const removeWatermark = () => {let id = '1.23452384164.123412415'if (document.getElementById(id) !== null) {document.body.removeChild(document.getElementById(id))}
}

登录页面取消水印 

我是通过登录后用户名是否存在来判断

  updated(){let name=localStorage.getItem("userName")if (name) {setWaterMark('',name)}else{setWaterMark('','')}},mounted() {},destroyed() {removeWatermark();},

因为是在app.vue文件中添加的，生命周期函数部分只执行一次。需要在组件更新时候进行判断

也可以利用路由守卫，在路由中进行判断