vue2添加背景水印-手动实现（无组件模式）

1. App.vue

<template><div id="app" class="app"><router-view></router-view></div>
</template><script>
export default {mounted() {this.updateWatermark();// 监听路由变化this.$router.afterEach(() => {this.$nextTick(() => {this.ensureWatermarkAndTable();});});// 监听 DOM 变化，确保表格背景实时调整this.observeDOM();},data() {return {watermarkText: "",user: {},};},methods: {updateWatermark() {let curUser = sessionStorage.getItem("curUser");if (curUser) {try {const userData = JSON.parse(curUser);this.watermarkText = `${userData.systemUsers.nickname}(${userData.systemRoleList[0].name})`;} catch (e) {console.error("解析 curUser 失败:", e);this.watermarkText