js实现框选功能?
用html实现以下功能：
1，页面中间有一个1000*600的画布
2，画布上按住鼠标左键拖拽可以实现一个框选的功能
3，鼠标松开后选框消失
要求：框选用div实现，不要用canvas
回答：
<!DOCTYPE html><html>
<head>
<meta charset="UTF-8">
<title>Div Selection Demo</title>
<style>
#canvas {
position: relative;
width: 1000px;
height: 600px;
border: 1px solid black;
}
#selection-box {
position: absolute;
border: 2px dashed blue; /* 将边框样式改成虚线 */
display: none;
}
</style>
</head>
<body>
<div id="canvas">
<div id="selection-box"></div>
</div>
<script>
const canvas = document.getElementById('canvas');
const selectionBox = document.getElementById('selection-box');
let isDragging = false;
let startX = 0;
let startY = 0;
canvas.addEventListener('mousedown', e => {
isDragging = true;
startX = e.clientX - canvas.offsetLeft;
startY = e.clientY - canvas.offsetTop;
selectionBox.style.left = startX + 'px';
selectionBox.style.top = startY + 'px';
selectionBox.style.width = '0px';
selectionBox.style.height = '0px';
selectionBox.style.display = 'block';
});
canvas.addEventListener('mousemove', e => {
if (isDragging) {
const currentX = e.clientX - canvas.offsetLeft;
const currentY = e.clientY - canvas.offsetTop;
const width = currentX - startX;
const height = currentY - startY;
selectionBox.style.width = Math.abs(width) + 'px';
selectionBox.style.height = Math.abs(height) + 'px';
selectionBox.style.left = Math.min(currentX, startX) + 'px';
selectionBox.style.top = Math.min(currentY, startY) + 'px';
}
});
canvas.addEventListener('mouseup', e => {
isDragging = false;
selectionBox.style.display = 'none';
});
</script>
</body>
</html>
回答：
<!DOCTYPE html><html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
#canvas-container {
background-color: aqua;
}
#selection-box {
background: rgba(0, 0, 255, 0.2);
}
</style>
</head>
<body>
<div id="canvas-container" style="position: relative; width: 1000px; height: 600px;">
<div id="selection-box" style="position: absolute; border: 2px solid black; display: none;"></div>
</div>
<script>
const canvasContainer = document.getElementById("canvas-container");
const selectionBox = document.getElementById("selection-box");
let isDragging = false;
let startX, startY, endX, endY;
canvasContainer.addEventListener("mousedown", (e) => {
isDragging = true;
startX = e.clientX - canvasContainer.offsetLeft;
startY = e.clientY - canvasContainer.offsetTop;
});
canvasContainer.addEventListener("mousemove", (e) => {
if (isDragging) {
endX = e.clientX - canvasContainer.offsetLeft;
endY = e.clientY - canvasContainer.offsetTop;
selectionBox.style.display = "block";
selectionBox.style.left = Math.min(endX, startX) + "px";
selectionBox.style.top = Math.min(endY, startY) + "px";
selectionBox.style.width = Math.abs(endX - startX) + "px";
selectionBox.style.height = Math.abs(endY - startY) + "px";
}
});
canvasContainer.addEventListener("mouseup", (e) => {
isDragging = false;
selectionBox.style.display = "none";
// Add code here to select the elements within the rectangle
});
</script>
</body>
</html>
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