angular 禁止回退

import { CanDeactivate } from "@angular/router";
// import { UserLockComponent } from "../lock/lock.component";
import {UserLockComponent} from ‘./lock.component‘;

export class BackGuard implements CanDeactivate<UserLockComponent>{
  //第一个参数 范型类型的组件
  //根据当前要保护组件 的状态 判断当前用户是否能够离开
  canDeactivate(component: UserLockComponent){
 if(component.backType == ‘history‘){
   return false;
 }else if(component.backType == ‘submit‘){
   return true;
 }else{
   return false;
 }
    // return window.confirm(‘你还没有保存，确定要离开吗？‘);
  }
}