JS Lab

如何用 JavaScript 在浏览器中弹窗
如何在 JavaScript 中制作鼠标滑过按钮改变背景颜色
如何在 JS 中点击按钮使数字增加
如何在 JS 中循环打印多少次

HTML

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>JS Lab</title><link rel="stylesheet" href="css/style.css">
</head>
<body><button class="btn" onclick="alertBtn()">Alert Button</button><hr><button class="btn" id="hoverButton">Hover Button</button><hr><button class="btn" id="increaseButton">Incrementing Button</button><span id="number" class="even">0</span><hr><p class="p-loop">For Loops: Print "Hello!" 10 times</p><div id="container"></div>
</body>
<script async src="js/lab.js"></script>
</html>

CSS

body{font-family:Arial; font-size:16px;}
hr{border:1px dashed #ddd;}
.btn{padding:8px 20px; margin: 5px 0;border-radius: 100px;border:1px solid #aaa;}
.btn:hover{background:#fff;}
#hoverButton{background:green; color:#fff; border:0;}
#number{font-size: 20px; margin-left:15px;}
.p-loop{font-weight: bold;}
.odd {color: blue;}
.even {color: red;}

JavaScript

// Alert 
function alertBtn() {alert("Hello world!");
}// Hover Button
let hoverButton = document.getElementById('hoverButton');
hoverButton.onmouseover = function() {this.style.backgroundColor = 'orange'; 
};
hoverButton.onmouseout = function() {this.style.backgroundColor = ''; 
};// Incrementing Button
document.getElementById('increaseButton').addEventListener('click', function() {let numberElement = document.getElementById('number');let currentNumber = parseInt(numberElement.textContent, 10);currentNumber += 1; let newClass = currentNumber % 2 === 0 ? 'even' : 'odd';numberElement.textContent = currentNumber;numberElement.className = newClass;
});// For Loops
for (let i = 0; i < 10; i = i + 1) {document.getElementById('container').append('Hello! ');
}// Change Font Color
function changeFontColor() {let changeButton = document.getElementById("pColor"); let color = changeButton.style.color;if (color == "red") { changeButton.style.color = 'blue';} else {changeButton.style.color = 'red';}
}