1 在服务中设置公共缓存

1.创建缓存服务
ng g service service/storage
set(key:string,value:any){
    localStorage.setItem(key,JSON.stringify(value))
  }
  get(key:string){
   let search:any = localStorage.getItem(key)
   return JSON.parse(search)
  }
  remove(key:string){
    localStorage.removeItem(key)
  }
2.在app.module.ts中去引入服务
import { StorageService } from './service/storage.service'
providers: [StorageService],
3.在需要的组件中引入
import {StorageService} from '../../../service/StorageService.service'
constructor(public httprequest:HttprequestService) { }
statechange(){
    this.storage.set('todolist',this.todolist)
  }
  ngOnInit() {
    let search:any = this.storage.get('todolist')
    if(search){
      this.todolist = search
    }
  }