很多时候在后台管理系统中，有在页面中添加员工姓名的水印的需求，保证系统的安全性。可以定一个如下的方法，提供两种方案供选择，第二种更简洁，也是我目前使用的，很稳定。

第一种方案：

watermark(settings) {
      //默认设置
      var defaultSettings={
          watermark_txt:settings.watermark_txt,
          watermark_x:20,//水印起始位置x轴坐标
          watermark_y:20,//水印起始位置Y轴坐标
          watermark_rows:5,//水印行数
          watermark_cols:10,//水印列数
          watermark_x_space:100,//水印x轴间隔
          watermark_y_space:100,//水印y轴间隔
          watermark_color:'#aaa',//水印字体颜色
          watermark_alpha:0.4,//水印透明度
          watermark_fontsize:'15px',//水印字体大小
          watermark_font:'微软雅黑',//水印字体
          watermark_width:210,//水印宽度
          watermark_height:80,//水印长度
          watermark_angle:15//水印倾斜度数
      };
      //采用配置项替换默认值，作用类似jquery.extend
      if(arguments.length===1&&typeof arguments[0] ==="object" )
      {
          var src=arguments[0]||{};
          for(var keyS in src)
          {
              if(src[keyS]&&defaultSettings[keyS]&&src[keyS]===defaultSettings[keyS])
                  continue;
              else if(src[keyS])
                  defaultSettings[keyS]=src[keyS];
          }
      }
    
      var oTemp = document.createDocumentFragment();
    
      //获取页面最大宽度
      var page_width = Math.max(document.body.scrollWidth,document.body.clientWidth);
      var cutWidth = page_width*0.0150;
      var page_width=page_width-cutWidth;
      //获取页面最大高度
      var page_height = Math.max(document.body.scrollHeight,document.body.clientHeight)+650;
      // var page_height = document.body.scrollHeight+document.body.scrollTop;
      //如果将水印列数设置为0，或水印列数设置过大，超过页面最大宽度，则重新计算水印列数和水印x轴间隔
      if (defaultSettings.watermark_cols == 0 || (parseInt(defaultSettings.watermark_x + defaultSettings.watermark_width *defaultSettings.watermark_cols + defaultSettings.watermark_x_space * (defaultSettings.watermark_cols - 1)) > page_width)) {
          defaultSettings.watermark_cols = parseInt((page_width-defaultSettings.watermark_x+defaultSettings.watermark_x_space) / (defaultSettings.watermark_width + defaultSettings.watermark_x_space) - 1);
          defaultSettings.watermark_x_space = parseInt((page_width - defaultSettings.watermark_x - defaultSettings.watermark_width * defaultSettings.watermark_cols) / (defaultSettings.watermark_cols - 1) - 10);
      }
      //如果将水印行数设置为0，或水印行数设置过大，超过页面最大长度，则重新计算水印行数和水印y轴间隔
      if (defaultSettings.watermark_rows == 0 || (parseInt(defaultSettings.watermark_y + defaultSettings.watermark_height * defaultSettings.watermark_rows + defaultSettings.watermark_y_space * (defaultSettings.watermark_rows - 1)) > page_height)) {
          defaultSettings.watermark_rows = parseInt((defaultSettings.watermark_y_space + page_height - defaultSettings.watermark_y) / (defaultSettings.watermark_height + defaultSettings.watermark_y_space));
          defaultSettings.watermark_y_space = parseInt(((page_height - defaultSettings.watermark_y) - defaultSettings.watermark_height * defaultSettings.watermark_rows) / (defaultSettings.watermark_rows - 1));
      }
      var x;
      var y;
      for (var i = 0; i < defaultSettings.watermark_rows; i++) {
          y = defaultSettings.watermark_y + (defaultSettings.watermark_y_space + defaultSettings.watermark_height) * i;
          for (var j = 0; j < defaultSettings.watermark_cols; j++) {
              x = defaultSettings.watermark_x + (defaultSettings.watermark_width + defaultSettings.watermark_x_space) * j;
    
              var mask_div = document.createElement('div');
              mask_div.id = 'mask_div' + i + j;
              mask_div.className = 'mask_div';
              mask_div.appendChild(document.createTextNode(defaultSettings.watermark_txt));
              //设置水印div倾斜显示
              mask_div.style.webkitTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
              mask_div.style.MozTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
              mask_div.style.msTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
              mask_div.style.OTransform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
              mask_div.style.transform = "rotate(-" + defaultSettings.watermark_angle + "deg)";
              mask_div.style.visibility = "";
              mask_div.style.position = "absolute";
              mask_div.style.left = x + 'px';
              mask_div.style.top = y + 'px';
              mask_div.style.overflow = "hidden";
              mask_div.style.zIndex = "9999";
              mask_div.style.pointerEvents='none';//pointer-events:none  让水印不遮挡页面的点击事件
              //mask_div.style.border="solid #eee 1px";
              mask_div.style.opacity = defaultSettings.watermark_alpha;
              mask_div.style.fontSize = defaultSettings.watermark_fontsize;
              mask_div.style.fontFamily = defaultSettings.watermark_font;
              mask_div.style.color = defaultSettings.watermark_color;
              mask_div.style.textAlign = "center";
              mask_div.style.width = defaultSettings.watermark_width + 'px';
              mask_div.style.height = defaultSettings.watermark_height + 'px';
              mask_div.style.display = "block";
              oTemp.appendChild(mask_div);
          };
      };
      document.body.appendChild(oTemp);
    },
// 定义时间
timeFormate() {
        let date = new Date();
        let Y = date.getFullYear();
        let M= (date.getMonth() + 1) < 10? '0' + (date.getMonth() + 1) :date.getMonth() + 1 ;
        let D = date.getDate()<10? '0'+ date.getDate():date.getDate();
        return Y +M +D
      }

最后在页面的created生命周期函数中调用即可

created() {
    if(this.userInfo) {
      let userId = this.userInfo.nickname ;
      this.watermark({watermark_txt:userId + " " + this.timeFormate()});
    }
  },

最终呈现的页面效果如下：

 或者在mian.js中引入方法：

router.afterEach((to) => {
  const title = getToken()
  if (title) {
    Watermark(title) // 设置水印title
  }
})

第二种方案：

第一步：创建js文件

let watermark = {}

let setWatermark = (str) => {
  let id = '1.23452384164.123412415'

  if (document.getElementById(id) !== null) {
    document.body.removeChild(document.getElementById(id))
  }

  let can = document.createElement('canvas')
  can.width = 500
  can.height = 250

  let cans = can.getContext('2d')
  cans.rotate(-20 * Math.PI / 180)
  cans.font = '14px Microsoft JhengHei'
  cans.fillStyle = '#dddddd'
  cans.textAlign = 'left'
  cans.textBaseline = 'Middle'
  cans.fillText(str, can.width / 3, can.height / 2)

  let div = document.createElement('div')
  div.id = id
  div.style.pointerEvents = 'none'
  div.style.top = '70px'
  div.style.left = '0px'
  div.style.position = 'fixed'
  div.style.zIndex = '100000'
  div.style.width = document.documentElement.clientWidth - 100 + 'px'
  div.style.height = document.documentElement.clientHeight - 100 + 'px'
  div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat'
  document.body.appendChild(div)
  return id
}

// 该方法只允许调用一次
watermark.set = (str) => {
  let id = setWatermark(str)
  setInterval(() => {
    if (document.getElementById(id) === null) {
      id = setWatermark(str)
    }
  }, 500)
  window.onresize = () => {
    setWatermark(str)
  }
}

export default watermark

第二步：引入并调用

import watermark from '../../libs/watermark'

watermark.set(JSON.parse(Cookies.get("userInfo")).nickname);

效果如下：