Javascript '；JSON解析错误无法识别的令牌'<''；来自React Native'；的POST请求出错；s分量

请纠正我在这个问题上的基本错误，并帮助我解决这个问题。我将非常感谢。

为了纠正您的“基本错误”

是的，似乎返回的是html而不是JSON。现在我知道了为什么这个特殊的字符是
，这个问题已经解决了。URL中肯定有错误。谢谢@NeilLunni，我遇到了同样的问题，我已经用postman测试了我的api，我还测试了浏览器上的url/端点，它返回json文件。有什么问题吗？@JonasModie，如果你得到
import React from 'react';
import {StyleSheet, Text, View, TextInput, KeyboardAvoidingView, Keyboard, TouchableOpacity, AsyncStorage} from 'react-native';
import {StackNavigator} from 'react-navigation';
export default class Broadcast extends React.Component {
    constructor(props){
        super(props);
        this.state ={
            username: ''
        }
    }
    componentDidMount(){
        this._loadInitialState().done();
    }
    _loadInitialState=async()=>{
        var user= await AsyncStorage.getItem('user');
        console.log(user+'*********************')
        if(user!==null){
            this.setState({
                username:user
            });
        }
    }
    render() {
        this.broadcastList();
    return ( 
        <KeyboardAvoidingView behavior='padding' style={styles.wrapper}>
            <View style={styles.container}>
                <Text style={styles.header}>Broadcast Page</Text>
            </View>
        </KeyboardAvoidingView>
    );
  }
  broadcastList=()=>{
      console.log(this.state.username);
        fetch(`http://192.168.137.1:3000/getBroadcastList?id=${this.state.username}`,{
            method:'POST',
            headers:{
                'Accept':'application/json',
                'Content-Type':'application/json',
            },
            body: JSON.stringify({
            })
        }) //backend IP :')
        .then((response)=> response.json())
        .then((res)=>{
            if(res.success===true){
                AsyncStorage.setItem('changeInBroadcastList',false);
                AsyncStorage.setItem('broadcastList',res.broadcastList);

            }
            else{
                AsyncStorage.setItem('loginSuccess',false);
                alert(res.message);
            }
        })
        .done();
    }
}
const styles=StyleSheet.create({
    wrapper:{
        flex:1
    },
    container:{
        flex:1,
        alignItems: 'center',
        justifyContent: 'center',
        backgroundColor: '#fff0f0',
        paddingLeft: 40,
        paddingRight: 40
    },
    header:{
        fontSize: 24,
        marginBottom:60,
        color:'#000000',
        fontWeight: 'bold',
    },
    textInput:{
        alignSelf: 'stretch',
        padding:16,
        marginBottom:20,
        backgroundColor:'#fff',
    },
    btn:{
        alignSelf: 'stretch',
        backgroundColor:'#f0f0ff',
        padding:20,
        alignItems: 'center',
    }
})

JSON Parse error: Unrecognized token '<'
tryCallOne
    Z:\saic\crossplatform\brodSaic\node_modules\promise\setimmediate\core.js:37:14
<unknown>
    Z:\saic\crossplatform\brodSaic\node_modules\promise\setimmediate\core.js:123:25
<unknown>
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\Core\Timers\JSTimers.js:297:23
_callTimer
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\Core\Timers\JSTimers.js:154:6
_callImmediatesPass
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\Core\Timers\JSTimers.js:202:17
callImmediates
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\Core\Timers\JSTimers.js:466:11
__callImmediates
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:329:4
<unknown>
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:147:6
__guardSafe
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:316:6
flushedQueue
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:146:17
invokeCallbackAndReturnFlushedQueue
    Z:\saic\crossplatform\brodSaic\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:142:11