原生JS怎么实现汇率转换功能

     



Exchange Rate Calculator
Choose the currency and the amounts to get the exchange rate
 
  AED ARS AUD BGN BRL BSD CAD CHF CLP CNY COP CZK DKK DOP EGP EUR FJD GBP GTQ HKD HRK HUF IDR ILS INR ISK JPY KRW KZT MXN MYR NOK NZD PAB PEN PHP PKR PLN PYG RON RUB SAR SEK SGD THB TRY TWD UAH USD UYU VND ZAR   
 
  Swap  
 
 
  AED ARS AUD BGN BRL BSD CAD CHF CLP CNY COP CZK DKK DOP EGP EUR FJD GBP GTQ HKD HRK HUF IDR ILS INR ISK JPY KRW KZT MXN MYR NOK NZD PAB PEN PHP PKR PLN PYG RON RUB SAR SEK SGD THB TRY TWD UAH USD UYU VND ZAR   

:root {
	--primary-color: #5fbaa7;
}
* {
	box-sizing: border-box;
}
body {
	background-color: #f4f4f4;
	font-family: Arial, Helvetica, sans-serif;
	display: flex;
	flex-direction: column;
	align-items: center;
	justify-content: center;
	height: 100vh;
	margin: 0;
	padding: 20px;
}
h2 {
	color: var(--primary-color);
}
p {
	text-align: center;
}
.btn {
	color: #fff;
	background: var(--primary-color);
	cursor: pointer;
	border-radius: 5px;
	font-size: 12px;
	padding: 5px 12px;
}
.money-img {
	width: 150px;
}
.currency {
	padding: 40px 0;
	display: flex;
	align-items: center;
	justify-content: space-between;
}
.currency select {
	padding: 10px 20px 10px 10px;
	-moz-appearance: none;
	-webkit-appearance: none;
	appearance: none;
	border: 1px solid #dedede;
	font-size: 16px;
	background: transparent;
	background-image: url('data:image/svg+xml;
	charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%2229 2.4%22%20height%3D%22292.4%22%3E%3Cpath%20fill%3D%22%20000002%22%20d%3D%22M287%2069.4a17.6%2017.6%200%200%200-13-5.4H18.4c-5%200-9.3%201.8-12.9%205.4A17.6%2017.6%200%200%200%200%2082.2c0%205%201.8%209.3%205.4%2012.9l128%20127.9c3.6%203.6%207.8%205.4%2012.8%205.4s9.2-1.8%2012.8-5.4L287%2095c3.5-3.5%205.4-7.8%205.4-12.8%200-5-1.9-9.2-5.5-12.8z%22%2F%3E%3C%2Fsvg%3E');
	background-position: right 10px top 50%, 0, 0;
	background-size: 12px auto, 100%;
	background-repeat: no-repeat;
}
.currency input {
	border: 0;
	background: transparent;
	font-size: 30px;
	text-align: right;
}
.swap-rate-container {
	display: flex;
	align-items: center;
	justify-content: space-between;
}
.rate {
	color: var(--primary-color);
	font-size: 14px;
	padding: 0 10px;
}
select:focus,
input:focus,
button:focus {
	outline: 0;
}
@media (max-width: 600px) {
	.currency input {
	width: 200px;
}
}

// 获取货币1对象
let currencyEl_one = document.getElementById("currency-one");
// 获取货币2对象
let currencyEl_two = document.getElementById("currency-two");
// 获取货币1对应的汇率对象
let amountEl_one = document.getElementById("amount-one");
// 获取货币2对应的汇率对象
let amountEl_two = document.getElementById("amount-two");
// 获取提示框对应的对象
let rateEl = document.getElementById("rate");

// 检查初始状态下 是否需要换算汇率
getData();

// 货币2发生变化时 触发的事件
currencyEl_two.onchange = getData;

// 货币1发生变化时 触发的事件
currencyEl_one.onchange = getData;

// 获取按钮 货币1和货币2是否都有值
let btn = document.getElementById("swap");

// 点击交换按钮时 触发的事件
btn.onclick = function() {
  // console.log("!!!");
  let currency_one = currencyEl_one.value;
  let currency_two = currencyEl_two.value;
  // 定义临时变量
  let temp = currency_one;
  // 交换货币1和货币2的value
  currencyEl_one.value = currency_two;
  currencyEl_two.value = temp;
  // 并且交换货币1和货币2对应的汇率
  currency_one = currency_two;
  currency_two = temp;

  fetch(`https://api.exchangerate-api.com/v4/latest/${currency_one}`)
    .then(res => res.json())
    .then(data => {
      const rate = data.rates[currency_two];
      rateEl.innerText = `1 ${currency_one} = ${rate} ${currency_two}`;
      amountEl_two.value = (amountEl_one.value * rate).toFixed(2);
    });

};

// 得到汇率
function getData() {
    let currency_one = currencyEl_one.value;
    let currency_two = currencyEl_two.value;
    fetch(`https://api.exchangerate-api.com/v4/latest/${currency_one}`)
      .then(res => res.json())
      .then(data => {
        const rate = data.rates[currency_two];
        rateEl.innerText = `1 ${currency_one} = ${rate} ${currency_two}`;
        amountEl_two.value = (amountEl_one.value * rate).toFixed(2);

      });
}