给前端局部界面（比如弹框里的内容）添加水印，亲测有效

function watermark(settings) {

var ele = document.getElementById("myBody");

//默认设置
var defaultSettings = {
watermark_txt: "机密材料 不得外泄",
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: 20, //水印行数
watermark_cols: 20, //水印列数
watermark_x_space: 100, //水印x轴间隔
watermark_y_space: 50, //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: 20 //水印倾斜度数
};

  var oTemp = document.createDocumentFragment();
//获取页面最大宽度
  var page_width = Math.max(ele.scrollWidth, ele.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(ele.scrollHeight, ele.clientHeight) ;
//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));
    defaultSettings.watermark_x_space = parseInt((page_width - defaultSettings.watermark_x - defaultSettings.watermark_width * defaultSettings.watermark_cols) / (defaultSettings.watermark_cols - 1));
  }
//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";
//让水印不遮挡页面的点击事件
      mask_div.style.pointerEvents = 'none';
      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);
    };
  };
  ele.appendChild(oTemp);

}


使用：

watermark（{"watermark_text":"机密材料 不得外泄"}）

 整个界面添加水印

安装watermark-dom插件

npm install watermark-dom

在组件中引入

import watermark from 'watermark-dom'

然后使用