js实现烟花

使用Canvas实现烟花效果

通过HTML5的Canvas元素结合JavaScript可以创建动态烟花效果。以下是一个基础实现方案：

<canvas id="fireworksCanvas"></canvas>

const canvas = document.getElementById('fireworksCanvas');
const ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

const particles = [];
const colors = ['#ff0000', '#ffff00', '#00ff00', '#00ffff', '#0000ff', '#ff00ff'];

function createFirework(x, y) {
  const particleCount = 100;
  for (let i = 0; i < particleCount; i++) {
    const angle = Math.random() * Math.PI * 2;
    const speed = Math.random() * 5 + 2;
    particles.push({
      x,
      y,
      vx: Math.cos(angle) * speed,
      vy: Math.sin(angle) * speed,
      color: colors[Math.floor(Math.random() * colors.length)],
      radius: Math.random() * 3 + 1,
      alpha: 1,
      decay: Math.random() * 0.015 + 0.01
    });
  }
}

function updateParticles() {
  for (let i = particles.length - 1; i >= 0; i--) {
    const p = particles[i];
    p.x += p.vx;
    p.y += p.vy;
    p.vy += 0.05;
    p.alpha -= p.decay;

    if (p.alpha <= 0) {
      particles.splice(i, 1);
    }
  }
}

function drawParticles() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  for (const p of particles) {
    ctx.globalAlpha = p.alpha;
    ctx.fillStyle = p.color;
    ctx.beginPath();
    ctx.arc(p.x, p.y, p.radius, 0, Math.PI * 2);
    ctx.fill();
  }
}

function animate() {
  updateParticles();
  drawParticles();
  requestAnimationFrame(animate);
}

canvas.addEventListener('click', (e) => {
  createFirework(e.clientX, e.clientY);
});

animate();

优化烟花效果的技巧

增加重力效果和随机性可以使烟花更逼真。修改粒子创建逻辑：

function createFirework(x, y) {
  const particleCount = 150;
  const hue = Math.floor(Math.random() * 360);

  for (let i = 0; i < particleCount; i++) {
    const angle = Math.random() * Math.PI * 2;
    const speed = Math.random() * 6 + 1;
    const saturation = 100 - Math.random() * 20;
    const lightness = 50 + Math.random() * 10;

    particles.push({
      x,
      y,
      vx: Math.cos(angle) * speed * (0.6 + Math.random() * 0.4),
      vy: Math.sin(angle) * speed * (0.6 + Math.random() * 0.4),
      color: `hsl(${hue}, ${saturation}%, ${lightness}%)`,
      radius: Math.random() * 4 + 1,
      alpha: 1,
      decay: Math.random() * 0.02 + 0.01,
      gravity: 0.05 + Math.random() * 0.03
    });
  }
}

自动发射烟花功能

添加定时自动发射功能，使烟花无需点击也能自动展示：

function autoFire() {
  const x = Math.random() * canvas.width;
  const y = Math.random() * canvas.height * 0.5;
  createFirework(x, y);
  setTimeout(autoFire, Math.random() * 2000 + 1000);
}

autoFire();

性能优化建议

对于大量粒子，使用对象池技术可以提升性能：

const particlePool = [];
const maxParticles = 5000;

function getParticle() {
  if (particlePool.length > 0) {
    return particlePool.pop();
  }
  return {};
}

function recycleParticle(p) {
  if (particlePool.length < maxParticles) {
    particlePool.push(p);
  }
}

// 在updateParticles中修改回收逻辑
if (p.alpha <= 0) {
  recycleParticle(p);
  particles.splice(i, 1);
}

这些代码组合起来可以创建一个视觉效果丰富的烟花演示，支持点击触发和自动播放两种模式，并且考虑了性能优化。