javascript - 复杂 else if 梯子的替代方案

Question

我有一个返回名为 user_id 的值的函数。但有很多条件需要检查。

条件1:检查服务变量

条件2:如果否，从localstorage获取user_id

条件3:如果否，从本地存储获取firebase_uid，并调用函数findUserId(firebase_uid)，该函数将返回user_id

条件 4:如果否，从 firebase 获取 uid 并调用 findUserId(uid)

这是代码。

export class UserService {

  user_id : any;
  firebase_uid: any;
  id: any;

returnUser_id() {

    if(this.user_id) {

      return this.user_id
    }

    else {
      this.storageService.get('user_id').then(val =>{
        if(val) {
          this.user_id =val
          return this.user_id
        }

        else {
          this.storageService.get('firebase_uid').then(value =>{
            if(value) {
              this.firebase_uid = value

              this.findUserId(this.firebase_uid).subscribe(q =>{
                console.log(q)
                this.id = q;
                for(let i =0; i<this.id.length;i++) {
                  this.user_id = this.id[i].id

                  return this.user_id

                }


                this.storageService.set('user_id', this.user_id ).then(result => {
                  console.log('Data is saved');
                  }).catch(e => {
                  console.log("error: " + e);
                  });


              })

            }
            else { 
              this.afauth.authState.subscribe(user =>{
                if(user) {
                  this.firebase_uid = user.uid; 


                  this.storageService.set('firebase_uid', this.firebase_uid ).then(result => {
                    console.log('Data is saved');
                    }).catch(e => {
                    console.log("error: " + e);
                    });


                    this.findUserId(this.firebase_uid).subscribe(data =>{
                      this.id = data;

                      for(let i = 0 ;i<this.id.length; i++ ){
                        this.user_id = this.id[i].id
                        return this.user_id
                      }

                      this.storageService.set('user_id', this.user_id ).then(result => {
                        console.log('Data is saved');
                        }).catch(e => {
                        console.log("error: " + e);
                        });
                    })
                }
              })
            }


          }).catch(err =>{
            console.log(err)
          })
        }
      }).catch(err =>{
        console.log(err)
      })
    }

  }

}

findUserId函数

findUserId(uid): Observable<any> {
  return this.http.get<User[]>(this.user_url + 'users?filter[fields][id]=true&filter[where][firebase_uid]=' +uid )

}

这段代码非常复杂，难以理解。是否有传统 if else 语句的替代方案。

提前谢谢

Answer 1

有一些可重复的代码，因此我们可以将可重复的代码移至方法中并重用它。此外，我们可以简化我们的代码using async keywords .

if(this.user_id)   
    return this.user_id;
else {
    let user_id = await this.storageService.get('user_id');
    if (user_id)  
        return user_id;
    else {
        let firebase_uid = await this.storageService.get('firebase_uid');
        if (firebase_uid) {
            await reusableFindUserId(firebase_uid);

            if (this.user_id)
                await setStorageService();
        }        
        else { 
            let user = await this.afauth.authState();
            if (user) {
                this.firebase_uid = user.uid;
                await reusableFindUserId(firebase_uid);

                if (this.user_id)
                    await setStorageService();
            }
        })
      }
    }
}    

和可重用的方法:

async reusableFindUserId(firebase_uid){
    this.id = await this.findUserId(firebase_uid);
    for(let i =0; i<this.id.length;i++) {
        this.user_id = this.id[i].id;
        return this.user_id;
    }
}

async setStorageService() {
    return await this.storageService.set('user_id', this.user_id );
}