SyntaxError：提取请求中的输入意外结束

Question

我已经在python上设置了flask服务器，并成功将获取请求发送到了后端。但是，该代码在执行以下代码后返回错误。 LogInClick是调用引发错误的函数的函数。调用该函数后，网页将返回对象promise，woo，然后返回SyntaxError。我正在努力查找导致错误的原因，请您能帮助我吗？

我尝试检查一下括号以确保没有错位，但我无法解决问题。

 loginClick() {
        let a = this.state.IS.checkExists(this.state.username);
        alert(a);
        if (a === false) {
            alert("Username not found!");
        } else if (this.state.IS.checkPassword(this.state.password) === true){
            alert("Password incorrect");
        } else {
            alert("woooo");
            this.setState({
                loggedIn: true
            });
        }
        if (this.setState.loggedIn) {
            window.location.pathname = '/workspacehome';
        }
    }
async checkExists(user) {
        await postData(a.BASE_URL, {'u_n': user}) // THIS IS LINE 10
            .then(data => alert(JSON.stringify(data))) // JSON-string from `response.json()` call
            .catch(error => {
                console.log(error);
                alert(error);
            });
    }

let a = new Configuration();

function postData(url = '', data = {}) { //THIS IS LINE 47
    // Default options are marked with *
    return fetch(url, {
        method: 'POST', // *GET, POST, PUT, DELETE, etc.
        mode: 'no-cors', // no-cors, cors, *same-origin
        cache: 'no-cache', // *default, no-cache, reload, force-cache, only-if-cached
        credentials: 'same-origin', // include, *same-origin, omit
        headers: {
            'Content-Type': 'application/json',
            // 'Content-Type': 'application/x-www-form-urlencoded',
        },
        redirect: 'follow', // manual, *follow, error
        referrer: 'no-referrer', // no-referrer, *client
        body: JSON.stringify(data), // body data type must match "Content-Type" header
    })
        .then(response => response.json()); // parses JSON response into native Javascript objects
}
```javascript

SyntaxError: Unexpected end of input
    at item_service.js:47
    at async ItemService.checkExists (item_service.js:10)