HTML5跨年烟花动画效果

script var canvas document.getElementById cas var ocas document.createElement canvas var octx ocas.getContext2d var ctx canvas.getContext2d ocas.width canvas.width window.innerWidth ocas.heightcanvas.height700var bigbooms window.onload function initAnimate function initAnimate drawBg lastTime new Date animate var lastTime function animate ctx.save ctx.fillStyle rgba