提取API始终返回{"_U":0，"_ V":0，"_ W":null，"_ X":null} [英] fetch API always returns {"_U": 0, "_V": 0, "_W": null, "_X": null}

问题描述

下面的代码总是返回下面的有线对象

The below code always return the below wired object

{"_ U":0，"_ V":0，"_ W":null，"_ X":null}

{"_U": 0, "_V": 0, "_W": null, "_X": null}

作为回应.

这是我的代码

    getData = () => {
        fetch('http://192.168.64.1:3000/getAll',{
            method: 'GET',
            headers: {
                Accept: 'application/json',
                'Content-Type': 'application/json'
            }
        })
        .then((response) => {
            console.log('Response:')
            console.log(response.json())
            console.info('=================================')
        })
        .catch(err => console.error(err));

    } 

    componentDidMount(){
        this.getData();
    }

我正在使用node，express，Mysql作为后端和react-native前端

I am using node, express, Mysql as backend and react-native frontend

我的后端代码在这里

app.get('/getAll',(req,res) => {
    console.log('getAll method Called');
    con.query('select * from dummy',(err,results,fields) => {
        if(err) throw err;
        console.log('Response');
        console.log(results);
        res.send(results);
    });
});

上面的代码在控制台中提供了正确的输出，但fetch API却没有.

The above code gives correct output in console but fetch API is not.

我找不到解决我问题的方法.预先感谢.

i cant find solution for the my problem. Thanks in advance.

推荐答案

这表示您在解决承诺之前记录了承诺-当您执行以下操作时的结果: console.log(response.json())

That indicates that you are logging the promise before it resolves - the result of when you: console.log(response.json())

如何访问承诺回调值功能之外?

正如@Evert在注释中正确指出的，这是因为response.json()返回了一个Promise对象.

As @Evert rightfully pointed out in comments, this is because response.json() returns a promise object.

因此，您需要在调用 response.json()并记录已解决的承诺后，再链接一个附加的 .then().

So, you'll need to chain an additional .then() after you call response.json() where you log the resolved promise.

getData = () => {
    fetch('http://192.168.64.1:3000/getAll',{
        method: 'GET',
        headers: {
            Accept: 'application/json',
            'Content-Type': 'application/json'
        }
    })
    .then(response => response.json())
    .then(data => {
        console.log(data);
    })
    .catch(err => console.error(err));
} 

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