问为什么fetch API有时不被调用？

EN

    constructor(props) {
    super(props)



    if (props.auth === false) {
        props.history.push("/")
    }

    //clearing reduce expenser before filling it up from the database to avoid duplicate data
    this.props.dispatch(resetExpenseReducer())

    //calling api to get all the expenses
    const url = "http://localhost:8080/getExpenses?email=" + encodeURIComponent(props.email)
    let h = new Headers({
        "Authorization": "Bearer " + props.token
    })

    let req = new Request(url, {
        headers: h
    })

    fetch(req).then((response, error) => {

        response.json().then((data, error) => {

            //filling the expenses in the reducer one by one
            for (let i = 0; i < data.length; i++) {

                this.props.dispatch(addExpense({ description: data[i].description, note: data[i].note, amount: parseInt(data[i].amount), createdAt: parseInt(data[i].createdAt), id: data[i].id }))

            }

        }).catch((error)=>{
            console.log(error)
        })
    }).catch((error)=>{
        console.log(error)
    })

}