提醒空取

Question

我试图让fetch停止并在它返回errorMessage时发出警报， 所以()=>this.toggleModal()不会被执行。

    handleSubmit(event){
        const url = 'http://localhost:8000/issue/';
        var issueid = 13900;
        var issueid = document.getElementById("SearchTxt").value;
        if(issueid == 0){
            alert('Please insert IssueID or IssueKey')
        }else{
            var string2 = url+issueid;
            fetch(string2)
            .then(function(response) {
              return response.json();
            })
            .then((myJson) => this.setState({example: myJson},() => this.toggleModal()))
        }
}

当问题不存在时返回JSON：

{
    errorMessages: [
        "Issue Does Not Exist"
     ],
     errors: { },
}

Answer 1

如果您想取消return response.json();的执行，可以执行以下操作

handleSubmit(event){
    const url = 'http://localhost:8000/issue/';
    var issueid = document.getElementById("SearchTxt").value;
    if(issueid == 0 || issueid == "" || issueid == undefined || issueid == null){
        alert('Please insert IssueID or IssueKey')
        return;
    }
    var string2 = url+issueid;
    fetch(string2)
        .then(function(response) {
          const oJson = response.json();
          // your validation of the json
          if(oJson.hasOwnProperty("errorMessages") && oJson.errorMessages.includes("Issue Does Not Exist")
              return Promise.reject(oJson.errorMessages[0]); // maybe use a better way instead of this hardcoded index 

          // set state if everything was properly done
          this.setState({example: myJson},() => this.toggleModal())
        })
        .catch(error => {
            // do some alert stuff
            alert(error);
        });
}

Answer 2

我设法解决了这个问题：

     handleSubmit(event){
        const url = 'http://localhost:8000/issue/';
        var issueid = 13900;
        var issueid = document.getElementById("SearchTxt").value;
        if(issueid == 0){
            alert('Please insert IssueID or IssueKey')
        }else{
            var string2 = url+issueid;
            fetch(string2)
            .then(function(response) {
              return response.json();
            })
            .then((myJson) => this.conditionalChaining(myJson));
        }
}

conditionalChaining(myJson) {
    if (myJson.errorMessages == 'Issue Does Not Exist') {
        alert('Issue doesn´t exist')
    } else {
        this.setState({example: myJson},() => this.toggleModal());
    }
}