1. 前言
一年一度的圣诞节和考研即将来临，那么这篇文章将用到前端三大剑客 html + css + JS 来实现动态圣诞树！
2. 效果展示
在手机上还可以通过左右滑动来控制雪花的方向哦！
3. 准备
🍑 下载编译器
这里的话推荐使用 VScode（方便！）
🍑 下载插件
Auto Rename Tag：改善标签后自动完善
Chinses语言包：把编译器语言换成中文（默认英文）
open in browser：让代码在网页中打开，快捷键 Alt + B
4. 源码
以下源码都已经准备好了，大家复制即可。
🍑 HTML
代码示例
<!DOCTYPE html>
<html lang="en" >
<head>
<meta charset="UTF-8">
<title>CodePen - Christmas Tree and Snow</title>
<link rel="stylesheet" href="https://cdnjs.cloudflare.***/ajax/libs/meyer-reset/2.0/reset.min.css">
<link rel="stylesheet" href="./style.css">
</head>
<body>
<!-- partial:index.partial.html -->
<canvas id="canvas"></canvas>
<div class="overlay"></div>
<!-- partial -->
<script src="./script.js"></script>
</body>
</html>
🍑 JS
代码示例
// Particle Lib
function Particle(x, y, speed, angle) {
this.x = x;
this.y = y;
this.vx = Math.cos(angle || 0) * (speed || 0);
this.vy = Math.sin(angle || 0) * (speed || 0);
}
Particle.prototype.updatePosition = function () {
this.x += this.vx;
this.y += this.vy;
};
Particle.prototype.draw = function (ctx) {
ctx.fillStyle = this.color;
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, 2 * Math.PI, false);
ctx.fill();
};
// Snowing
var numOfSnowParticles = 100;
var snowParticles = [];
var windFromLeft = false;
var windFromRight = false;
function createSnowParticles() {
let particle = new Particle(Math.random() * screenWidth, -10, 1, 2 * Math.PI / 2 * Math.random());
particle.originalX = particle.x;
particle.originalY = particle.y;
particle.radius = 1 + Math.random() * 2;
particle.angle = 0;
particle.speed = .05;
particle.isDead = false;
particle.color = "white";
snowParticles.push(particle);
}
function drawSnowFrame() {
for (var i = 0; i < snowParticles.length; i++) {
let particle = snowParticles[i];
if (!particle.isDead) {
particle.updatePosition();
if (!windFromLeft && !windFromRight) {
particle.x = particle.originalX + Math.sin(particle.angle) * 10;
} else if (windFromLeft) {
particle.x += 2;
particle.originalX = particle.x;
} else if (windFromRight) {
particle.x -= 2;
particle.originalX = particle.x;
}
particle.y += .1;
particle.angle += particle.speed;
checkIfParticleTouchesADeadParticle(i);
checkIfParticleHitsGround(particle);
}
particle.draw(context);
}
}
function checkIfParticleHitsGround(particle) {
if (particle.y + particle.radius > screenHeight) {
particle.y = screenHeight - particle.radius;
particle.isDead = true;
}
}
function checkIfParticleTouchesADeadParticle(index) {
for (var i = index + 1; i < snowParticles.length; i++) {
if (snowParticles[i].isDead) {
let dx = snowParticles[index].x - snowParticles[i].x;
let dy = snowParticles[index].y - snowParticles[i].y;
let distance = Math.sqrt(Math.pow(dx, 2) + Math.pow(dy, 2));
if (distance <= snowParticles[index].radius + snowParticles[i].radius) {
snowParticles[index].isDead = true;
}
}
}
}
document.addEventListener('touchstart', handleTouchStart, false);
document.addEventListener('touchmove', handleTouchMove, false);
var xDown = null;
var yDown = null;
function handleTouchStart(evt) {
xDown = evt.touches[0].clientX;
yDown = evt.touches[0].clientY;
};
function handleTouchMove(evt) {
if (!xDown || !yDown) {
return;
}
var xUp = evt.touches[0].clientX;
var yUp = evt.touches[0].clientY;
var xDiff = xDown - xUp;
var yDiff = yDown - yUp;
if (Math.abs(xDiff) > Math.abs(yDiff)) {
if (xDiff > 0) {
windFromRight = true;
windFromLeft = false;
} else {
windFromLeft = true;
windFromRight = false;
}
} else {
windFromLeft = windFromRight = false;
}
xDown = null;
yDown = null;
};
// Tree
var treeParticles = [];
var treeColors = ['#199642', '#E44822', '#40B8E2', '#F7D231'];
function drawTreeFrame() {
for (var i = 0; i < treeParticles.length; i++) {
treeParticles[i].draw(context);
treeParticles[i].radius = 1 + Math.random() * 3;
}
if (treeParticles.length > 0) {
drawStar(centerX, screenHeight * .2, 5, 20, 10);
}
}
function getPixelData(imageData, x, y) {
let basePosition = (screenWidth * y + x) * 4;
return {
r: imageData.data[basePosition],
g: imageData.data[basePosition + 1],
b: imageData.data[basePosition + 2],
a: imageData.data[basePosition + 3] };
}
function drawStar(cx, cy, spikes, outerRadius, innerRadius) {
var rot = Math.PI / 2 * 3;
var x = cx;
var y = cy;
var step = Math.PI / spikes;
context.beginPath();
context.moveTo(cx, cy - outerRadius);
for (i = 0; i < spikes; i++) {
x = cx + Math.cos(rot) * outerRadius;
y = cy + Math.sin(rot) * outerRadius;
context.li***o(x, y);
rot += step;
x = cx + Math.cos(rot) * innerRadius;
y = cy + Math.sin(rot) * innerRadius;
context.li***o(x, y);
rot += step;
}
context.li***o(cx, cy - outerRadius);
context.closePath();
context.lineWidth = 5;
context.strokeStyle = 'yellow';
context.stroke();
context.fillStyle = 'lightyellow';
context.fill();
}
function initTree(text) {
context.clearRect(0, 0, screenWidth, screenHeight);
context.moveTo(centerX, screenHeight * .2);
context.li***o(centerX - 100, centerY + 100);
context.li***o(centerX + 100, centerY + 100);
context.fill();
var imageData = context.getImageData(0, 0, screenWidth, screenHeight);
context.clearRect(0, 0, screenWidth, screenHeight);
treeParticles.length = 0;
for (var i = 0; i < screenWidth; i += 10) {
for (j = 0; j < screenHeight; j += 10) {
let pixelData = getPixelData(imageData, i, j);
if (pixelData.a > 0) {
let particle = new Particle(i, j);
particle.color = treeColors[Math.floor(Math.random() * 5)];
particle.radius = 1 + Math.random() * 3;
treeParticles.push(particle);
}
}
}
}
//let canvas = document.querySelector('#canvas');
let context = canvas.getContext('2d');
let screenWidth = canvas.width = window.innerWidth;
let screenHeight = canvas.height = window.innerHeight;
var centerX = screenWidth * .5;
var centerY = screenHeight * .5;
drawFrame();
function drawFrame() {
context.clearRect(0, 0, screenWidth, screenHeight);
context.fillStyle = "black";
context.fillRect(0, 0, screenWidth, screenHeight);
context.fillStyle = "white";
context.font = "bold 50px Kaushan Script";
context.textAlign = "center";
context.fillText("Merry Christmas", centerX, screenHeight * .8);
drawTreeFrame();
drawSnowFrame();
requestAnimationFrame(drawFrame);
}
initTree('hello world');
setInterval(() => {
createSnowParticles();
}, 100);
🍑 CSS
代码示例
@import url("https://fonts.googleapis.***/css?family=Great+Vibes|Kaushan+Script");
body {
margin: 0;
}
.overlay {
position: fixed;
top: 0;
left: 0;
z-index: 10;
color: white;
width: 100%;
text-align: center;
padding: 5px;
font-family: "Avenir", "Helvetica";
}
5. 结语
属于 2022 的时间，不知不觉进入了倒计时！
准备多时的 “马拉松”，即将抵达终点！
时光不负有心人，星光不负赶路人。
祝大家圣诞快乐，也愿各位考研人一战成硕！！！
