已经设置的反应挂钩如何设置为另一个值

Question

这是我第一次使用 React hooks，我偶然发现了一个我无法解决的问题。 我正在使用formAmount挂钩来获取将其存储在state.amount中的输入值。 发生这种情况时，只要用户将其放入，该数量就应该减少到一个数字。问题是我无法在onChange事件中创建一个新数组，因为它对键的每个笔划进行编目并且它没有给出我是完整的数字，我不能直接在state.amount上设置它。 如何获得该数量并存储在数组中？

这是我的代码：

const Transactions = () => {
    const [state, setState] = useState([
        {
            expense: [],
            amount: [],
            id: ''
        }

    ])

    const [formExpense, setFormExpense] = useState('')
    const [formAmount, setFormAmount] = useState([])



    const handleSubmit = (e) => {
        e.preventDefault();

        addExpense()
        e.target.reset()
    }
    // add total of array of amount
    let sum = formAmount.reduce((accumulator, currentValue) => {
        { return accumulator += currentValue }
    }, 0)

    // push value of input to array
    const addExpense = (e) => {

        setState([...state, { expense: formExpense, amount: [...formAmount], id: Math.random() * 100 }])

    }


    return (
        <div className="transactions">

            <div className="expenses">
                <form onSubmit={handleSubmit}>
                    <input
                        type="text"
                        id="expense"
                        className="formfield"
                        name="expense"
                        placeholder="Expense..."
                        onChange={(e) => setFormExpense(e.target.value)}
                    />
                    <input
                        type="text"
                        id="amount"
                        className="formfield"
                        name="amount"
                        placeholder="Amount..."
                        onChange={(e) => setFormAmount([Number(e.target.value)])}
                    />
                    <button type="submit">Submit</button>
                </form>
            </div>
            <div className="finalbalance ">

                <div className="finalexpense final">
                    Total Expense
                    {'$' + sum.toLocaleString()}
                    {
                        state.map(stat => {
                            return (

                                <div key={stat.id}>

                                    <h3 className="outputexpense output">{stat.expense + stat.amount}</h3>
                                </div>


                            )
                        })
                    }

                </div>
            </div>
        </div>


    )
}

Answer 1

这是给你的答案。 我在这里也做了一个小提琴

 function Transaction(props){ const [listOfExpenses, setlistOfExpenses] = React.useState([]); const [expense, setExpense] = React.useState(""); const [amount, setAmount] = React.useState(0); const [totalExpenditure, setTotalExpenditure] = React.useState(0); const handleInputChange = (hookSetterMethod) => (e) =>{ let {value} = e.target; return hookSetterMethod(value); } const addExpense = (expenseObject) => { setlistOfExpenses([...listOfExpenses, expenseObject]) } const getTotalExpenditure = (listOfExpenses) => { if(listOfExpenses.length > 0) { let tempExpenseAmountList = listOfExpenses.map((expense, id)=>{ if(expense.amount) { return expense.amount; }else{ return 0; } }); return tempExpenseAmountList.reduce((accumulator, currentVal)=>{ return Number(accumulator) + Number(currentVal); }) } return 0; } React.useEffect(()=>{ setTotalExpenditure(getTotalExpenditure(listOfExpenses)); }, [listOfExpenses]) const handleFormSubmission = (e) =>{ e.preventDefault(); addExpense({ amount, expense }); } const renderExpenses = (expenseList) => { return expenseList.map((expense, id)=>{ return ( <tr key={id}> <td>{++id}</td> <td>{expense.expense}</td> <td>: ${expense.amount}</td> </tr> ) }); } return( <div> <div> <h1>Add your expenses below</h1> <form onSubmit={handleFormSubmission}> <div> <label>Expense</label> <input value={expense} onChange={handleInputChange(setExpense)} /> </div> <div> <label>Amount</label> <input value={amount} onChange={handleInputChange(setAmount)} /> </div> <div> <button type="submit">Add Expense</button> </div> </form> </div> <hr /> <div> <table> <tr> <th> <td>Id</td> <td>Expense</td> <td>Amount</td> </th> </tr> {renderExpenses(listOfExpenses)} <tr className="total"> <td>Total Expenses</td> <td>: ${totalExpenditure}</td> </tr> </table> </div> </div> ); } ReactDOM.render(<Transaction />, document.getElementById("root"));

 table{ margin-top: 15px; }.total{ display: table; border-top: 1px solid #434649; border-bottom: 2px double #434649; color: #f80000; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.0/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.0/umd/react-dom.production.min.js"></script> <div id="root"></div>