toLocaleString作用：在没有指定区域的基本使用时，返回使用默认的语言环境和默认选项格式化的字符串。可点击进入MDN查看

// 千分位分隔符指令
import { Directive, DirectiveBinding } from 'vue'

const thousandSeparator: Directive = {
  mounted(el: any, binding: DirectiveBinding) {
  // 获取文本
    const value = el.innerText
    if (value && !isNaN(Number(value))) { // 判断文本是不是数字
   // 对其进行转化
      el.innerText = Number(value).toLocaleString('en-US')
    }
  },
  updated(el: any, binding: DirectiveBinding) {
    const value = el.innerText
    if (value && !isNaN(Number(value))) {
      el.innerText = Number(value).toLocaleString('en-US')
    }
  }
}

export default {
  thousandSeparator
}

//在mian.ts中注册指令

import { createApp, Directive } from 'vue'
import pinia from './store/index'
import i18n from './i18n'
import router from './router/index'
import App from './App.vue'
// 引入指令文件
import directives from '@/utils/directives'


const app = createApp(App)
app.use(pinia).use(i18n()).use(router).mount('#app')

//  注册指令
Object.keys(directives).forEach(key => {
  //Object.keys() 返回一个数组，值是所有可遍历属性的key名
  app.directive(key, (directives as { [key: string]: Directive })[key]) //key是自定义指令名字；后面应该是自定义指令的值
})

效果