如何使用HTML，CSS和JavaScript构建技巧计算器
A Tip Calculator is a calculator that calculates a tip based on the percentage of the total bill.
小费计算器是根据总账单的百分比计算小费的计算器。
Let's build one now.
让我们现在建立一个。
第1步-HTML： (Step 1 - HTML:)
We create a form in order to enter the preferred amount:
我们创建一个表格以输入首选金额：
<!doctype html>
<html lang="en">
<head>
<title>Tip Calculator</title>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous">
</head>
<body class="bg-dark">
<div class="container">
<div class="row">
<div class="col-md-6 mx-auto">
<div class="card card-body text-center mt-5">
<h1 class="heading display-5 pb-3">Tip Calculator</h1>
<form id="tip-form">
<div class="form-group">
<div class="input-group">
<span class="input-group-addon">$</span>
<input type="number" class="form-control" id="billTotal" placeholder="Total Bill">
</div>
</div>
<div class="form-group tipPersent">
<div class="input-group">
<label for="">Tip:</label>
<input type="range" class="form-control" id="tipInput" value="0">
<span class="input-group-addon" id="tipOutput"></span>
</div>
</div>
</form>
<hr>
<!-- RESULTS -->
<div id="results" class="pt-4">
<h5>Results</h5>
<div class="form-group">
<div class="input-group">
<span class="input-group-addon">Tip amount</span>
<input type="number" class="form-control" id="tipAmount" disabled>
</div>
</div>
<div class="form-group">
<div class="input-group">
<span class="input-group-addon">Total Bill with Tip</span>
<input type="number" class="form-control" id="totalBillWithTip" disabled>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<!-- Optional JavaScript -->
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js" integrity="sha384-vFJXuSJphROIrBnz7yo7oB41mKfc8JzQZiCq4NCceLEaO4IHwicKwpJf9c9IpFgh" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js" integrity="sha384-alpBpkh1PFOepccYVYDB4do5UnbKysX5WZXm3XxPqe5iKTfUKjNkCk9SaVuEZflJ" crossorigin="anonymous"></script>
</body>
</html>第2步-CSS： (Step 2 - CSS:)
You design the style however you want. You can also use CSS to hide the results and show them through JavaScript after the user fills in the form:
您可以根据需要设计样式。 您还可以使用CSS隐藏结果，并在用户填写表单后通过JavaScript显示结果：
#results {
display:none;
}步骤3：JavaScript： (Step 3: JavaScript:)
We add an onchange event. The onchange event occurs when the user interacts with the form.
我们添加一个onchange事件。 当用户与表单交互时，会发生onchange事件。
This action will execute a function that computes the final bill amount based on the percentage tip, then returns the results.
该操作将执行一个函数，该函数根据百分比提示计算最终的帐单金额，然后返回结果。
document.querySelector('#tip-form').onchange = function(){
var bill = Number(document.getElementById('billTotal').value);
var tip = document.getElementById('tipInput').value;
document.getElementById('tipOutput').innerHTML = `${tip}%`;
var tipValue = bill * (tip/100)
var finalBill = bill + tipValue
console.log(finalBill)
var tipAmount = document.querySelector('#tipAmount')
var totalBillWithTip = document.querySelector('#totalBillWithTip')
tipAmount.value = tipValue.toFixed(2);
totalBillWithTip.value =finalBill.toFixed(2);
//Show Results
document.getElementById('results').style.display='block'
}You can see a working example and its code on Codepen.io.
您可以在Codepen.io上看到一个有效的示例及其代码。
翻译自: https://www.freecodecamp.org/news/how-to-build-a-tip-calculator-with-html-css-and-javascript/