如何讓這個更幹DRY

Question

JavaScript新手，只需要一些幫助，使這更幹。不知道，如果使用switch語句是要走的路...

.catch((err) => { 
    console.log(err) 
    let emailDup = 'user already exists' 
    let userDup = 'username already exists' 
    if (err.response.body.includes(emailDup)) { 
    this.setState({ 
     errMessage: errEmailDup, 
     error: true, 
     loading: false 
    }) 
    } else if (err.response.body.includes(userDup)) { 
    this.setState({ 
     errMessage: errUserDup, 
     error: true, 
     loading: false 
    }) 
    } else { 
    this.setState({ 
     errMessage: errDefault, 
     error: true, 
     loading: false 
    }) 
    } 
} 

Answer 1

下面的代碼易於閱讀和維護（添加更多的情況下是很容易以及）：

.catch((err) => { 
    let emailDup = 'user already exists'; 
    let userDup = 'username already exists'; 
    let errMessage; 

    if (err.response.body.includes(emailDup)) { 
     errMessage = errEmailDup; 

    } else if (err.response.body.includes(userDup)) { 
     errMessage = errUserDup; 

    } else { 
     errMessage = errDefault; 
    } 

    this.setState({ 
     errMessage: errMessage, 
     error: true, 
     loading: false 
    }); 
} 

Answer 2

您可以使用三元

.catch((err) => { 
    let emailDup = 'user already exists' 
    let userDup = 'username already exists' 
     this.setState({ 
      errMessage: err.response.body.includes(emailDup) ? errEmailDup : (err.response.body.includes(userDup) ? errUserDup : errDefault), 
      error: true, 
      loading: false 
     }) 
    }