我以为我一切都是正确的，我仍然无法弄清楚为什么这个函数没有按照它应该的方式工作。我有这个问题，代码有一个参考错误，但我不确定如何定义函数。我也把它通过W3验证器，但它没有告诉我任何东西。
<!DOCTYPE HTML>
<html lang="en-us">
<head>
<meta charset="utf-8">
<title>discount amount</title>
</head>
<body>
<script>
/* Input: purchase amount
* Processing: determine through if statements if they get a discount
* Output: final price after tax
*/
// Computes and returns a discounted purchase amount.
function getDiscountedAmount(purchase) {
var purchase =
parseInt(document.getElementById('purchase').value);
var dayOfWeek = new Date().getDay();
var output = document.querySelector("#output");
let rate;
if (purchase < 50) {
rate = 0.06;
} else if (purchase < 100 && [2, 3].includes(dayOfWeek)) {
rate = 0.06;
} else if (purchase < 500 && [2, 3].includes(dayOfWeek)) {
rate = 0.06;
}
let discount = purchase * rate;
return purchase - discount;
output.innerHTML = "$" + String(getDiscountedAmount(200));
}
</script>
Please enter your final price: <input type="text" id="purchase" size="5">
<br>
<button type="button" onclick="getDiscountedAmount(purchase)">discount?
</button>
<div id="output"></div>
</body>
</html>
你的函数的第一行已经是错误的，你试图从没有得到一个浮点数，你重写你的输入参数到函数
var purchase = parseFloat();
试题:
purchase = parseFloat(purchase);
以便使用您的输入参数。
我也不太确定你的日期比较dayOfWeek == (2, 3)，我不知道它是否有效，我以前从未见过，我个人使用[2, 3].includes(dayOfWeek)
最后你的函数返回一个值但是你在任何地方都看不到这个值，试着使用
console.log(getDiscountedAmount(200))或者其他价格
在输入和输出方面，您希望使用DOM操作来获取输入并显示输出。
如果您希望在"输出"中查看值
var output = document.querySelector("#output");
output.innerHTML = "$" + String(getDiscountedAmount(200));
将是一个简单的DOM机制，但它不是最干净的
还有一个技巧是将脚本标签放在正文的最后，因为您希望所有HTML元素都"定义"。首先，在您尝试访问它们之前
你的代码的一个更清晰的版本:
<!DOCTYPE HTML>
<html lang="en-us">
<head>
<meta charset="utf-8">
<title>discount amount</title>
</head>
<body>
Please enter your final price: <input type="text" id="myInput" size="5" /><br />
<button type="button" id="myButton">discount?</button>
<div id="myOutput"></div>
<script>
var myInput = document.querySelector("#myInput");
var myOutput = document.querySelector("#myOutput");
var myButton = document.querySelector("#myButton");
myButton.onclick = function() {
// Computes and returns a discounted purchase amount.
var purchase = parseFloat(myInput.value);
var dayOfWeek = new Date().getDay();
var rate;
if (purchase < 50) {
rate = 0.06;
} else if (purchase < 100 && [2, 3].includes(dayOfWeek)) {
rate = 0.06;
} else if (purchase < 1000) {
rate = 0.025;
} else {
rate = 0.03;
}
let discount = purchase * rate;
var finalPrice = purchase - discount;
output.innerHTML = "$" + String(finalPrice);
};
</script>
</body>
</html>
我改变了一些ID，并将onclick移动到您的JavaScript中，以获得更干净的代码，因为我们喜欢将HTML与JS分开
当您加载脚本时，您将获得一个Uncaught SyntaxError，因为您使用两个}关闭了函数。要解决这个问题，只需删除第31行。
在函数的第一行中，您使用的parseFloat();错误:
var purchase = parseFloat();
:
var purchase = parseFloat(purchase);
你需要得到你输入的数字。onclick事件中的getDiscountedAmount(purchase)不起作用。你可以这样写:
var purchase = document.getElementById("purchase").value; // get value from text field
purchase = parseFloat(purchase); // convert to float
最后你必须这样做来显示你输出的数字div:
let output = purchase - discount;
document.getElementById("output").innerText = output; // set discont into your output div
return output;
这是你的代码和我如何修复它:
<!DOCTYPE HTML>
<html lang="en-us">
<head>
<meta charset="utf-8">
<title>discount amount</title>
<script>
/* Input: purchase amount
* Processing: determine through if statements if they get a discount
* Output: final price after tax
*/
// Computes and returns a discounted purchase amount.
function getDiscountedAmount(purchase) {
var purchase = document.getElementById("purchase").value; // get value from text field
purchase = parseFloat(purchase); // convert to float
var dayOfWeek = new Date().getDay();
var rate;
if (purchase < 50) {
rate = 0.06;
}
else if (purchase < 100 && dayOfWeek ==(2,3)) {
rate = 0.06;
}
else if (purchase < 1000) {
rate = 0.025;
}
else {
rate = 0.03;
}
let discount = purchase * rate;
let output = purchase - discount;
document.getElementById("output").innerText = output; // set discont into your output div
return output;
}
</script>
</head>
<body>
Please enter your final price: <input type="text" id="purchase" size="5"><be>
<button type="button" onclick="getDiscountedAmount()">discount?</button>
<div id="output"></div>
</body>
</html>我没有改变你的返回语句和dayOfWeek，因为我不知道你到底想要如何使用它。
这是你要找的:
body{margin:0;padding:0;font-family:arial;background:rgb(30,30,30);height:100vh;width:100%}.wrapper{background:lightgrey;background:linear-gradient(318deg,rgba(217,123,123,1) 0%,rgba(135,249,255,1) 100%);width:80%;height:126px;position:relative;top:calc(50vh - 63px);left:10%;padding:3px;border-radius:12px}.content{background:rgb(80,80,80);background:rgba(0,0,0,.5);border-radius:10px;width:calc(100% - 24px);padding:12px}label{font-weight:700;color:#fff}input{width:calc(100% - 16px);margin-top:4px;padding:6px;border:2px solid #fff;border:2px solid rgba(0,0,0,.3);color:#fff;background:#fff;background:rgba(0,0,0,.5);border-radius:6px;font-size:14pt}::placeholder{color:#fff;color:rgba(255,255,255,.8)}input:focus{outline:none;border:2px solid #fff;border:3px solid rgba(0,0,0,.6);padding:5px}.output-container{display:inline-block;float:right;width:180px;padding:8px;color:#fff;background:#fff;background:rgba(0,0,0,.5);font-size:12pt;margin-top:4px;border-radius:6px;font-size:14pt}button{margin-top:4px;width:150px;border:0;border-radius:6px;padding:8px;background:gray;background:rgba(0,0,0,.6);color:#fff;font-weight:700;font-size:14pt;transition:0.25s ease}button:focus{outline:none;}button:hover{cursor:pointer;background:gray;background:rgba(0,0,0,.8)}@media only screen and (max-width:400px){.wrapper{width:calc(100% - 6px);height:auto;top:0;left:0;border-radius:0}.output-container,button{width:calc(50% - 12px)}}<!DOCTYPE HTML>
<html lang="en-us">
<head>
<meta charset="utf-8">
<title>discount amount</title>
</head>
<body>
<div class='wrapper'>
<div class='content'>
<label>Please enter your final price:</label><input type="text" autocomplete="off" placeholder='Enter price...' id="purchase" size="5">
<button type="button" onclick="getDiscountedAmount()">See discount</button>
<div class='output-container'>Total: <span id='output'>--</span></div>
</div>
</div>
<script>
//Get the output element
outputEl = document.getElementById("output");
function getDiscountedAmount() {
//Gets the value of your input
var purchase = parseFloat((document.getElementById('purchase').value).replace(/[^d]/g,""));
var dayOfWeek = new Date().getDay();
var rate;
if (purchase < 50) {
rate = 0.06;
} else if (purchase < 100 && [2, 3].includes(dayOfWeek)) {
rate = 0.06;
} else if (purchase < 500 && [2, 3].includes(dayOfWeek)) {
rate = 0.06;
}
else {
rate = 0.03;
}
let discount = purchase * rate;
let output = purchase - discount;
//Checks if output is a number.
if(isNaN(output)){
output = 'Not a number!';
} else{
output = '$' + output;
}
//Puts the output inside of your "output" <div>
outputEl.textContent = output;
}
</script>
</body>
</html>