特效描述：html5 canvas碎纸屑 空中飘落动画特效。canvas绘制空中飘落的纸屑动画特效。

代码结构

1. HTML代码

"use strict";

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Progress = function () {

function Progress() {

var param = arguments.length <= 0 || arguments[0] === undefined ? {} : arguments[0];

_classCallCheck(this, Progress);

this.timestamp = null;

this.duration = param.duration || Progress.CONST.DURATION;

this.progress = 0;

this.delta = 0;

this.progress = 0;

this.isLoop = !!param.isLoop;

this.reset();

}

Progress.prototype.reset = function reset() {

this.timestamp = null;

};

Progress.prototype.start = function start(now) {

this.timestamp = now;

};

Progress.prototype.tick = function tick(now) {

if (this.timestamp) {

this.delta = now - this.timestamp;

this.progress = Math.min(this.delta / this.duration, 1);

if (this.progress >= 1 && this.isLoop) {

this.start(now);

}

return this.progress;

} else {

return 0;

}

};

_createClass(Progress, null, [{

key: "CONST",

get: function get() {

return {

DURATION: 1000

};

}

}]);

return Progress;

}();

var Confetti = function () {

function Confetti(param) {

_classCallCheck(this, Confetti);

this.parent = param.elm || document.body;

this.canvas = document.createElement("canvas");

this.ctx = this.canvas.getContext("2d");

this.width = param.width || this.parent.offsetWidth;

this.height = param.height || this.parent.offsetHeight;

this.length = param.length || Confetti.CONST.PAPER_LENGTH;

this.yRange = param.yRange || this.height * 2;

this.progress = new Progress({

duration: param.duration,

isLoop: true

});

this.rotationRange = typeof param.rotationLength === "number" ? param.rotationRange : 10;

this.speedRange = typeof param.speedRange === "number" ? param.speedRange : 10;

this.sprites = [];

this.canvas.style.cssText = ["display: block", "position: absolute", "top: 0", "left: 0", "pointer-events: none"].join(";");

this.render = this.render.bind(this);

this.build();

this.parent.append(this.canvas);

this.progress.start(performance.now());

requestAnimationFrame(this.render);

}

Confetti.prototype.build = function build() {

for (var i = 0; i < this.length; ++i) {

var canvas = document.createElement("canvas"),

ctx = canvas.getContext("2d");

canvas.width = Confetti.CONST.SPRITE_WIDTH;

canvas.height = Confetti.CONST.SPRITE_HEIGHT;

canvas.position = {

initX: Math.random() * this.width,

initY: -canvas.height - Math.random() * this.yRange

};

canvas.rotation = this.rotationRange / 2 - Math.random() * this.rotationRange;

canvas.speed = this.speedRange / 2 + Math.random() * (this.speedRange / 2);

ctx.save();

ctx.fillStyle = Confetti.CONST.COLORS[Math.random() * Confetti.CONST.COLORS.length | 0];

ctx.fillRect(0, 0, canvas.width, canvas.height);

ctx.restore();

this.sprites.push(canvas);

}

};

Confetti.prototype.render = function render(now) {

var progress = this.progress.tick(now);

this.canvas.width = this.width;

this.canvas.height = this.height;

for (var i = 0; i < this.length; ++i) {

this.ctx.save();

this.ctx.translate(this.sprites[i].position.initX + this.sprites[i].rotation * Confetti.CONST.ROTATION_RATE * progress, this.sprites[i].position.initY + progress * (this.height + this.yRange));

this.ctx.rotate(this.sprites[i].rotation);

this.ctx.drawImage(this.sprites[i], -Confetti.CONST.SPRITE_WIDTH * Math.abs(Math.sin(progress * Math.PI * 2 * this.sprites[i].speed)) / 2, -Confetti.CONST.SPRITE_HEIGHT / 2, Confetti.CONST.SPRITE_WIDTH * Math.abs(Math.sin(progress * Math.PI * 2 * this.sprites[i].speed)), Confetti.CONST.SPRITE_HEIGHT);

this.ctx.restore();

}

requestAnimationFrame(this.render);

};

_createClass(Confetti, null, [{

key: "CONST",

get: function get() {

return {

SPRITE_WIDTH: 9,

SPRITE_HEIGHT: 16,

PAPER_LENGTH: 100,

DURATION: 8000,

ROTATION_RATE: 50,

COLORS: ["#EF5350", "#EC407A", "#AB47BC", "#7E57C2", "#5C6BC0", "#42A5F5", "#29B6F6", "#26C6DA", "#26A69A", "#66BB6A", "#9CCC65", "#D4E157", "#FFEE58", "#FFCA28", "#FFA726", "#FF7043", "#8D6E63", "#BDBDBD", "#78909C"]

};

}

}]);

return Confetti;

}();

(function () {

var DURATION = 8000,

LENGTH = 120;

new Confetti({

width: window.innerWidth,

height: window.innerHeight,

length: LENGTH,

duration: DURATION

});

setTimeout(function () {

new Confetti({

width: window.innerWidth,

height: window.innerHeight,

length: LENGTH,

duration: DURATION

});

}, DURATION / 2);

})();