如何在react中动态添加表行?

wgxvkvu9  于 2021-09-13  发布在  Java
关注(0)|答案(1)|浏览(462)

我目前正在使用react制作一个贷款计算器应用程序,我想根据用户从输入的类型range中选择的贷款期限向表中添加多行。每一行都将显示还款日期以及根据用户希望获得的贷款金额和利率计算的相应值。我目前正在使用带有react的引导v5。

import React, { useState } from "react";
import "./App.css";

function App() {
  const date = new Date();
  const today = date.getDate() + "/" + (date.getMonth() + 1) + "/" + date.getFullYear();
  const [loan, setLoan] = useState(1000);
  const [duration, setDuration] = useState(1);
  const [interest, setInterest] = useState(0);
  const [dates, setDates] = useState([]);

  const getInterest = () => {
    let interestedAmount = (loan * interest) / 100;
    interestedAmount /= duration;
    return Math.round((interestedAmount + Number.EPSILON) * 100) / 100;
  };

  const getPrincipal = () => {
    let dividedAmount = loan / duration;
    return Math.round((dividedAmount + Number.EPSILON) * 100) / 100;
  };

  const getTotalRepayment = () => {
    return getInterest() + getPrincipal();
  };

  return (
    <React.Fragment>
      <header>
        <h1>Your Loan</h1>
      </header>
      <main>
        <form>
          <div className="row g-3 align-items-center">
            <div className="col-auto">
              <label htmlFor="loan-input" className="form-label">
                Loan Amount (£) : {loan}
              </label>
            </div>
            <div className="col-auto">
              <input
                type="range"
                value={loan}
                min="1000"
                max="200000"
                step="1000"
                className="form-range"
                id="loan-input"
                onChange={e => setLoan(e.target.value)}
              />
            </div>
          </div>
          <div className="row g-3 align-items-center">
            <div className="col-auto">
              <label htmlFor="duration-input" className="form-label">
                Duration (in Months) : {duration}
              </label>
            </div>
            <div className="col-auto">
              <input
                type="range"
                value={duration}
                min="1"
                max="60"
                step="1"
                className="form-range"
                id="duration-input"
                onChange={e => setDuration(e.target.value)}
              />
            </div>
          </div>
        </form>
        <div className="row g-3 align-items-center">
          <div className="col-auto">
            <label htmlFor="interest-range" className="form-label">
              Interest Rate (%) : {interest}
            </label>
          </div>
          <div className="col-auto">
            <input
              type="range"
              value={interest}
              min="0"
              max="10"
              step="1"
              className="form-range"
              id="interest-range"
              onChange={e => setInterest(e.target.value)}
            />
          </div>
          <table className="table">
            <thead>
              <tr>
                <th scope="col">Repayment Date</th>
                <th scope="col">Principal</th>
                <th scope="col">Interest</th>
                <th scope="col">Total Repayment</th>
              </tr>
            </thead>
            <tbody>
              {
                <tr>
                  <td>{today}</td>
                  <td>{getPrincipal()}</td>
                  <td>{getInterest()}</td>
                  <td>{getTotalRepayment()}</td>
                </tr>
              }
            </tbody>
          </table>
        </div>
      </main>
    </React.Fragment>
  );
}

export default App;

我的想法是,当用户设置持续时间时,我会创建一个函数来生成一个日期数组并将其Map。然而,我担心的是,如果用户更改了持续时间,表是否会根据更改添加或删除行?

3vpjnl9f

3vpjnl9f1#

你可以使用 useEffect 钩子在用户每次更改持续时间值时创建一个日期数组。然后,您可以简单地Map这个数组以显示所需的行数。
这意味着您不需要设置“今天”日期,因为它将在第一次渲染之前运行的useeffect挂钩中设置。
最终的代码应该如下所示:

import React, { useState, useEffect } from "react";

function App() {
    const [loan, setLoan] = useState(1000);
    const [duration, setDuration] = useState(1);
    const [interest, setInterest] = useState(0);
    const [dates, setDates] = useState([]);

    const getInterest = () => {
        let interestedAmount = (loan * interest) / 100;
        interestedAmount /= duration;
        return Math.round((interestedAmount + Number.EPSILON) * 100) / 100;
    };

    const getPrincipal = () => {
        let dividedAmount = loan / duration;
        return Math.round((dividedAmount + Number.EPSILON) * 100) / 100;
    };

    const getTotalRepayment = () => {
        return getInterest() + getPrincipal();
    };

    useEffect(() => {
        let datesArray = [];

        for (let i = 0; i < duration; i++) {
            let date = new Date();
            date = new Date(date.setMonth(date.getMonth() + i));
            datesArray.push(
                date.getDate() + "/" + (date.getMonth() + 1) + "/" + date.getFullYear()
            );
        }

        setDates(datesArray);
    }, [duration]);

    return (
        <React.Fragment>
            <header>
                <h1>Your Loan</h1>
            </header>
            <main>
                <form>
                    <div className='row g-3 align-items-center'>
                        <div className='col-auto'>
                            <label htmlFor='loan-input' className='form-label'>
                                Loan Amount (£) : {loan}
                            </label>
                        </div>
                        <div className='col-auto'>
                            <input
                                type='range'
                                value={loan}
                                min='1000'
                                max='200000'
                                step='1000'
                                className='form-range'
                                id='loan-input'
                                onChange={(e) => setLoan(e.target.value)}
                            />
                        </div>
                    </div>
                    <div className='row g-3 align-items-center'>
                        <div className='col-auto'>
                            <label htmlFor='duration-input' className='form-label'>
                                Duration (in Months) : {duration}
                            </label>
                        </div>
                        <div className='col-auto'>
                            <input
                                type='range'
                                value={duration}
                                min='1'
                                max='60'
                                step='1'
                                className='form-range'
                                id='duration-input'
                                onChange={(e) => setDuration(e.target.value)}
                            />
                        </div>
                    </div>
                </form>
                <div className='row g-3 align-items-center'>
                    <div className='col-auto'>
                        <label htmlFor='interest-range' className='form-label'>
                            Interest Rate (%) : {interest}
                        </label>
                    </div>
                    <div className='col-auto'>
                        <input
                            type='range'
                            value={interest}
                            min='0'
                            max='10'
                            step='1'
                            className='form-range'
                            id='interest-range'
                            onChange={(e) => setInterest(e.target.value)}
                        />
                    </div>
                    <table className='table'>
                        <thead>
                            <tr>
                                <th scope='col'>Repayment Date</th>
                                <th scope='col'>Principal</th>
                                <th scope='col'>Interest</th>
                                <th scope='col'>Total Repayment</th>
                            </tr>
                        </thead>
                        <tbody>
                            {dates.map((date, index) => (
                                <tr key={index}>
                                    <td>{date}</td>
                                    <td>{getPrincipal()}</td>
                                    <td>{getInterest()}</td>
                                    <td>{getTotalRepayment()}</td>
                                </tr>
                            ))}
                        </tbody>
                    </table>
                </div>
            </main>
        </React.Fragment>
    );
}

export default App;

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