[2092] ReferenceError : "window is not defined"

code: header.vue:

export default {
  data(){
    return {
      msgShadeHeight: window.innerHeight, // 消息遮罩，点击消息旁边生成的遮罩
      //...
    }
  },
}

could u please tell me whats the correct way to use "window" in data ? thank u very much!