（一）小案例银行家应用程序-介绍

案例示例如下所示：

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登录之后就会出现下面所示：
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项目案例流程图如下
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● 首先我们建立四个账号对象，用于登录

const account1 = {
  owner: 'ItShare',
  movements: [200, 450, -400, 3000, -650, -130, 70, 1300],
  interestRate: 1.2, // %
  pin: 1111,
};

const account2 = {
  owner: 'Jessica Davis',
  movements: [5000, 3400, -150, -790, -3210, -1000, 8500, -30],
  interestRate: 1.5,
  pin: 2222,
};

const account3 = {
  owner: 'Steven Thomas Williams',
  movements: [200, -200, 340, -300, -20, 50, 400, -460],
  interestRate: 0.7,
  pin: 3333,
};

const account4 = {
  owner: 'Sarah Smith',
  movements: [430, 1000, 700, 50, 90],
  interestRate: 1,
  pin: 4444,
};

● 上述我们模拟数据都是来自与Web API，再将四个账户数据存储到一个数组中

const accounts = [account1, account2, account3, account4];

● 其中HTML代码如下

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <link rel="shortcut icon" type="image/png" href="icon.png" />

    <link
      href="https://fonts.googleapis.com/css?family=Poppins:400,500,600&display=swap"
      rel="stylesheet"
    />

    <link rel="stylesheet" href="style.css" />
    <title>Bankist</title>
  </head>
  <body>
    <!-- TOP NAVIGATION -->
    <nav>
      <p class="welcome">Log in to get started</p>
      <img src="logo.png" alt="Logo" class="logo" />
      <form class="login">
        <input
          type="text"
          placeholder="user"
          class="login__input login__input--user"
        />
        <!-- In practice, use type="password" -->
        <input
          type="text"
          placeholder="PIN"
          maxlength="4"
          class="login__input login__input--pin"
        />
        <button class="login__btn">&rarr;</button>
      </form>
    </nav>

    <main class="app">
      <!-- BALANCE -->
      <div class="balance">
        <div>
          <p class="balance__label">Current balance</p>
          <p class="balance__date">
            As of <span class="date">05/03/2037</span>
          </p>
        </div>
        <p class="balance__value">0000€</p>
      </div>

      <!-- MOVEMENTS -->
      <div class="movements">
        <div class="movements__row">
          <div class="movements__type movements__type--deposit">2 deposit</div>
          <div class="movements__date">3 days ago</div>
          <div class="movements__value">4 000€</div>
        </div>
        <div class="movements__row">
          <div class="movements__type movements__type--withdrawal">
            1 withdrawal
          </div>
          <div class="movements__date">24/01/2037</div>
          <div class="movements__value">-378€</div>
        </div>
      </div>

      <!-- SUMMARY -->
      <div class="summary">
        <p class="summary__label">In</p>
        <p class="summary__value summary__value--in">0000€</p>
        <p class="summary__label">Out</p>
        <p class="summary__value summary__value--out">0000€</p>
        <p class="summary__label">Interest</p>
        <p class="summary__value summary__value--interest">0000€</p>
        <button class="btn--sort">&downarrow; SORT</button>
      </div>

      <!-- OPERATION: TRANSFERS -->
      <div class="operation operation--transfer">
        <h2>Transfer money</h2>
        <form class="form form--transfer">
          <input type="text" class="form__input form__input--to" />
          <input type="number" class="form__input form__input--amount" />
          <button class="form__btn form__btn--transfer">&rarr;</button>
          <label class="form__label">Transfer to</label>
          <label class="form__label">Amount</label>
        </form>
      </div>

      <!-- OPERATION: LOAN -->
      <div class="operation operation--loan">
        <h2>Request loan</h2>
        <form class="form form--loan">
          <input type="number" class="form__input form__input--loan-amount" />
          <button class="form__btn form__btn--loan">&rarr;</button>
          <label class="form__label form__label--loan">Amount</label>
        </form>
      </div>

      <!-- OPERATION: CLOSE -->
      <div class="operation operation--close">
        <h2>Close account</h2>
        <form class="form form--close">
          <input type="text" class="form__input form__input--user" />
          <input
            type="password"
            maxlength="6"
            class="form__input form__input--pin"
          />
          <button class="form__btn form__btn--close">&rarr;</button>
          <label class="form__label">Confirm user</label>
          <label class="form__label">Confirm PIN</label>
        </form>
      </div>

      <!-- LOGOUT TIMER -->
      <p class="logout-timer">
        You will be logged out in <span class="timer">05:00</span>
      </p>
    </main>

    <!-- <footer>
      &copy; by Jonas Schmedtmann. Don't claim as your own :)
    </footer> -->

    <script src="script.js"></script>
  </body>
</html>

● CSS代码如下
/*

 * Use this CSS to learn some intersting techniques,
 * in case you're wondering how I built the UI.
 * Have fun! 😁
 */

* {
  margin: 0;
  padding: 0;
  box-sizing: inherit;
}

html {
  font-size: 62.5%;
  box-sizing: border-box;
}

body {
  font-family: "Poppins", sans-serif;
  color: #444;
  background-color: #f3f3f3;
  height: 100vh;
  padding: 2rem;
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 2rem;
}

.welcome {
  font-size: 1.9rem;
  font-weight: 500;
}

.logo {
  height: 5.25rem;
}

.login {
  display: flex;
}

.login__input {
  border: none;
  padding: 0.5rem 2rem;
  font-size: 1.6rem;
  font-family: inherit;
  text-align: center;
  width: 12rem;
  border-radius: 10rem;
  margin-right: 1rem;
  color: inherit;
  border: 1px solid #fff;
  transition: all 0.3s;
}

.login__input:focus {
  outline: none;
  border: 1px solid #ccc;
}

.login__input::placeholder {
  color: #bbb;
}

.login__btn {
  border: none;
  background: none;
  font-size: 2.2rem;
  color: inherit;
  cursor: pointer;
  transition: all 0.3s;
}

.login__btn:hover,
.login__btn:focus,
.btn--sort:hover,
.btn--sort:focus {
  outline: none;
  color: #777;
}

/* MAIN */
.app {
  position: relative;
  max-width: 100rem;
  margin: 4rem auto;
  display: grid;
  grid-template-columns: 4fr 3fr;
  grid-template-rows: auto repeat(3, 15rem) auto;
  gap: 2rem;

  /* NOTE This creates the fade in/out anumation */
  opacity: 0;
  transition: all 1s;
}

.balance {
  grid-column: 1 / span 2;
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 2rem;
}

.balance__label {
  font-size: 2.2rem;
  font-weight: 500;
  margin-bottom: -0.2rem;
}

.balance__date {
  font-size: 1.4rem;
  color: #888;
}

.balance__value {
  font-size: 4.5rem;
  font-weight: 400;
}

/* MOVEMENTS */
.movements {
  grid-row: 2 / span 3;
  background-color: #fff;
  border-radius: 1rem;
  overflow: scroll;
}

.movements__row {
  padding: 2.25rem 4rem;
  display: flex;
  align-items: center;
  border-bottom: 1px solid #eee;
}

.movements__type {
  font-size: 1.1rem;
  text-transform: uppercase;
  font-weight: 500;
  color: #fff;
  padding: 0.1rem 1rem;
  border-radius: 10rem;
  margin-right: 2rem;
}

.movements__date {
  font-size: 1.1rem;
  text-transform: uppercase;
  font-weight: 500;
  color: #666;
}

.movements__type--deposit {
  background-image: linear-gradient(to top left, #39b385, #9be15d);
}

.movements__type--withdrawal {
  background-image: linear-gradient(to top left, #e52a5a, #ff585f);
}

.movements__value {
  font-size: 1.7rem;
  margin-left: auto;
}

/* SUMMARY */
.summary {
  grid-row: 5 / 6;
  display: flex;
  align-items: baseline;
  padding: 0 0.3rem;
  margin-top: 1rem;
}

.summary__label {
  font-size: 1.2rem;
  font-weight: 500;
  text-transform: uppercase;
  margin-right: 0.8rem;
}

.summary__value {
  font-size: 2.2rem;
  margin-right: 2.5rem;
}

.summary__value--in,
.summary__value--interest {
  color: #66c873;
}

.summary__value--out {
  color: #f5465d;
}

.btn--sort {
  margin-left: auto;
  border: none;
  background: none;
  font-size: 1.3rem;
  font-weight: 500;
  cursor: pointer;
}

/* OPERATIONS */
.operation {
  border-radius: 1rem;
  padding: 3rem 4rem;
  color: #333;
}

.operation--transfer {
  background-image: linear-gradient(to top left, #ffb003, #ffcb03);
}

.operation--loan {
  background-image: linear-gradient(to top left, #39b385, #9be15d);
}

.operation--close {
  background-image: linear-gradient(to top left, #e52a5a, #ff585f);
}

h2 {
  margin-bottom: 1.5rem;
  font-size: 1.7rem;
  font-weight: 600;
  color: #333;
}

.form {
  display: grid;
  grid-template-columns: 2.5fr 2.5fr 1fr;
  grid-template-rows: auto auto;
  gap: 0.4rem 1rem;
}

/* Exceptions for interst */
.form.form--loan {
  grid-template-columns: 2.5fr 1fr 2.5fr;
}
.form__label--loan {
  grid-row: 2;
}
/* End exceptions */

.form__input {
  width: 100%;
  border: none;
  background-color: rgba(255, 255, 255, 0.4);
  font-family: inherit;
  font-size: 1.5rem;
  text-align: center;
  color: #333;
  padding: 0.3rem 1rem;
  border-radius: 0.7rem;
  transition: all 0.3s;
}

.form__input:focus {
  outline: none;
  background-color: rgba(255, 255, 255, 0.6);
}

.form__label {
  font-size: 1.3rem;
  text-align: center;
}

.form__btn {
  border: none;
  border-radius: 0.7rem;
  font-size: 1.8rem;
  background-color: #fff;
  cursor: pointer;
  transition: all 0.3s;
}

.form__btn:focus {
  outline: none;
  background-color: rgba(255, 255, 255, 0.8);
}

.logout-timer {
  padding: 0 0.3rem;
  margin-top: 1.9rem;
  text-align: right;
  font-size: 1.25rem;
}

.timer {
  font-weight: 600;
}

● 在此之前，我们要将我们所有需要的元素存储到变量中，方便我们后续使用

const labelWelcome = document.querySelector('.welcome');
const labelDate = document.querySelector('.date');
const labelBalance = document.querySelector('.balance__value');
const labelSumIn = document.querySelector('.summary__value--in');
const labelSumOut = document.querySelector('.summary__value--out');
const labelSumInterest = document.querySelector('.summary__value--interest');
const labelTimer = document.querySelector('.timer');

const containerApp = document.querySelector('.app');
const containerMovements = document.querySelector('.movements');

const btnLogin = document.querySelector('.login__btn');
const btnTransfer = document.querySelector('.form__btn--transfer');
const btnLoan = document.querySelector('.form__btn--loan');
const btnClose = document.querySelector('.form__btn--close');
const btnSort = document.querySelector('.btn--sort');

const inputLoginUsername = document.querySelector('.login__input--user');
const inputLoginPin = document.querySelector('.login__input--pin');
const inputTransferTo = document.querySelector('.form__input--to');
const inputTransferAmount = document.querySelector('.form__input--amount');
const inputLoanAmount = document.querySelector('.form__input--loan-amount');
const inputCloseUsername = document.querySelector('.form__input--user');
const inputClosePin = document.querySelector('.form__input--pin');