javascript - 如何检查以确保在React中单击按钮时填写表格？

Question

我有一个按钮，可以根据用户提供的数字进行计算，并将结果填充到页面中。相同的按钮还将产品保存到数据库中，同时还用数据库中的那些相同产品直观地填充页面。因此，基本上，它显示了用户在字段中输入的任何内容的总数和先前的总数。我的问题是我想包括错误处理，以便如果数字不是0或NaN(因为它们没有填写所有表格)，它将引发警报，也不会将数据推送到数据库。这是我的尝试，并且不起作用，如果结果为NaN，它仍会显示该结果并将NaN值 push 数据库，我该如何实现？尝试如下:

handleClick = (event, billInfo) => {
event.preventDefault();
const dbRef = firebase.database().ref();

const result =
  (billInfo.amount / billInfo.group) * (billInfo.tip / 100 + 1);

// ATTEMPT START ======

result === NaN
  ? alert("Please fill all forms!")
  : dbRef.push({
      result: result.toFixed(2),
      name: billInfo.name,
    });

// ATTEMPT END ======

this.setState({
  total: result.toFixed(2),
});

这是带有链接到主app.js的按钮的表单组件:

class inputForm extends Component {
  constructor() {
    super();
    this.state = {
      name: "",
      group: "",
      amount: "",
      tip: "",
    };
  }

  handleChange = (event) => {
    this.setState({
      [event.target.name]: event.target.value,
    });
  };

  clearForm = (event) => {
    event.preventDefault();

    this.setState({
      name: "",
      group: "",
      amount: "",
      tip: "",
    });
  };

  render() {
    return (
      <form className="tipApp">
        <div>
          <label htmlFor="groupName">
            <i class="fas fa-id-card"></i>Group Name?
          </label>
          <input
            onChange={this.handleChange}
            type="text"
            id="groupName"
            value={this.state.name}
            placeholder="Name your group"
            name="name"
          />
        </div>

        <div>
          <label htmlFor="groupSize">
            <i class="fas fa-users"></i>How many?
          </label>
          <input
            onChange={this.handleChange}
            type="number"
            id="groupSize"
            value={this.state.group}
            min="1"
            step="1"
            placeholder="Add the group size"
            name="group"
            required
          />
        </div>

        <div>
          <label htmlFor="billAmount">
            <i class="fas fa-receipt"></i>How much?
          </label>
          <input
            onChange={this.handleChange}
            type="number"
            id="billAmount"
            value={this.state.amount}
            min="0"
            step=".01"
            placeholder="Add the bill total"
            name="amount"
            required
          />
        </div>

        <div>
          <label htmlFor="tipAmount">
            <i class="fas fa-heart"></i>Tip?
          </label>
          <input
            onChange={this.handleChange}
            type="number"
            id="tipAmount"
            value={this.state.tip}
            min="10"
            step="5"
            placeholder="Add the tip %"
            name="tip"
          />
        </div>

        <button onClick={(event) => this.props.getTotal(event, this.state)}>
          Split it!
        </button>
        <button onClick={this.clearForm}>Reset</button>
      </form>
    );
  }
}

这是我尝试对其进行错误处理的完整app.js主文件:

class App extends Component {
  constructor() {
    super();
    this.state = {
      bills: [],
      total: 0,
    };
  }

  componentDidMount() {
    const dbRef = firebase.database().ref();

    // Event listener that watches the database
    dbRef.on("value", (snapshot) => {
      const firebaseData = snapshot.val();

      const billData = [];

      for (const bill in firebaseData) {
        billData.push({
          id: bill,
          name: firebaseData[bill].name,
          value: firebaseData[bill].result,
        });
      }
      this.setState({
        bills: billData,
      });
    });
  }

  handleClick = (event, billInfo) => {
    event.preventDefault();
    const dbRef = firebase.database().ref();

    const result =
      (billInfo.amount / billInfo.group) * (billInfo.tip / 100 + 1);

    result === NaN
      ? alert("Please fill all forms!")
      : dbRef.push({
          result: result.toFixed(2),
          name: billInfo.name,
        });

    this.setState({
      total: result.toFixed(2),
    });
  };

  deleteBill = (billId) => {
    const dbRef = firebase.database().ref();

    dbRef.child(billId).remove();
  };

  render() {
    return (
      <div className="wrapper">
        <h1 className="logoName">Spl|tr</h1>
        <h3>Bill Splitting App</h3>

        <Form getTotal={this.handleClick} />
        <h2>${this.state.total}</h2>

        <h3>Previous Bills</h3>
        <Bills receipts={this.state.bills} delete={this.deleteBill} />
      </div>
    );
  }
}

这是Bills.js组件，该组件在页面上的单击按钮下方的表格下方填充了之前的项目:

const Bills = (props) => {
  return (
    <ul>
      {props.receipts.map((bill) => {
        return (
          <li key={bill.id}>
            <p>{bill.name}</p>
            <p>${bill.value}</p>
            <button onClick={() => props.delete(bill.id)}>
              <i class="fas fa-times-circle"></i>
            </button>
          </li>
        );
      })}
    </ul>
  );
};

Answer 1

您的处理程序会更新状态，无论是否获得有效结果。一个小的重构应该允许一个有效的结果并推送到数据库并更新状态或一个无效的结果和警报。 0和NaN均为假值，因此您可以简单地检查result是否为真/假。

handleClick = (event, billInfo) => {
  event.preventDefault();
  const dbRef = firebase.database().ref();

  const result =
    (billInfo.amount / billInfo.group) * (billInfo.tip / 100 + 1);

  if (result) {
    dbRef.push({
      result: result.toFixed(2),
      name: billInfo.name,
    });
    this.setState({
      total: result.toFixed(2),
    });
  } else {
    alert("Please fill all forms!")
  }
};