手写particles

 var canvas = document.getElementById('canvas');
    var ctx = canvas.getContext('2d');

    var Grewer = {
        init: function() {
            this.getWindowSize();
            canvas.width = this.w;
            canvas.height = this.h;
            this.num = 50;
            this.range = 100;
            this.arr = [];
            this.add();

        },
        getWindowSize: function() {
            //获取窗口宽度
            if (window.innerWidth) { //兼容火狐，谷歌,safari等浏览器
                this.w = window.innerWidth;
            } else if ((document.body) && (document.body.clientWidth)) { //兼容IE浏览器
                this.w = document.body.clientWidth;
            }

            //获取窗口高度
            if (window.innerHeight) {
                this.h = window.innerHeight;
            } else if ((document.body) && (document.body.clientHeight)) {
                this.h = document.body.clientHeight;
            }
        },
        update: function(obj) {
            obj.x += obj.vx;
            obj.y += obj.vy;

            if (obj.x < 0 || obj.x > this.w) {
                obj.vx *= -1;
            }
            if (obj.y < 0 || obj.y > this.h) {
                obj.vy *= -1;
            }
        },
        add: function() {

            var i = this.num;
            while (i--) {
                var particles = {
                    x: (Math.random() * this.w) | 0,
                    y: (Math.random() * this.h) | 0,
                    vx: (Math.random() - .5) * 1,
                    vy: (Math.random() - .5) * 1,
                }
                this.arr.push(particles);
            }
        },
        checkDist: function(a, b, dist) {
            var x = a.x - b.x,
                y = a.y - b.y;

            return x * x + y * y <= dist * dist;
        },
        print: function(obj) {
            ctx.beginPath();
            ctx.arc(obj.x, obj.y, 2, 0, 2 * Math.PI);
            ctx.fillStyle = '#ddd';
            ctx.fill();
        }

    }
    var G = Object.create(Grewer);
    G.init();
    var Ganim = function() {
        window.requestAnimationFrame(Ganim);

        ctx.fillStyle = '#fff';
        ctx.fillRect(0, 0, G.w, G.h);

        var length = G.num;
        for (var i = 0; i < length; i++) {
            var o1 = G.arr[i]
            G.update(o1);
            G.print(o1);

            for (var j = i + 1; j < length; ++j) {

                var o2 = G.arr[j];
                if (G.checkDist(o1, o2, G.range)) {
                    ctx.strokeStyle = '#ddd';
                    ctx.beginPath();
                    ctx.moveTo(o1.x, o1.y);
                    ctx.lineTo(o2.x, o2.y);
                    ctx.stroke();
                }
            }

        }
    }
    Ganim();

旧版本

demo:https://grewer.github.io/JsDemo/particles/

github:https://github.com/Grewer/JsDemo/tree/master/particles

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var Grewer = {
    init: function() {
        this.getWindowSize();
        canvas.width = this.w;
        canvas.height = this.h;
        this.num = 70;
        this.range = 80;
        this.arr = [];
        this.add();
    },
    getWindowSize: function() {
        //获取窗口宽度
        if (window.innerWidth) { //兼容火狐，谷歌,safari等浏览器
            this.w = window.innerWidth;
        } else if ((document.body) && (document.body.clientWidth)) { //兼容IE浏览器
            this.w = document.body.clientWidth;
        }

        //获取窗口高度
        if (window.innerHeight) {
            this.h = window.innerHeight;
        } else if ((document.body) && (document.body.clientHeight)) {
            this.h = document.body.clientHeight;
        }
    },
    update: function(obj) {
        obj.x += obj.vx;
        obj.y += obj.vy;

        if (obj.x < 0 || obj.x > this.w) {
            obj.vx *= -1;
        }
        if (obj.y < 0 || obj.y > this.h) {
            obj.vy *= -1;
        }
    },
    add: function() {

        var i = this.num;
        while (i--) {
            var particles = {
                x: (Math.random() * this.w) | 0,
                y: (Math.random() * this.h) | 0,
                vx: (Math.random() - .5) * 1,
                vy: (Math.random() - .5) * 1,
                r: ((Math.random() * 2) | 0) + 1
            }
            this.arr.push(particles);
        }
    },
    checkDist: function(a, b, dist) {
        var x = a.x - b.x,
            y = a.y - b.y;

        return x * x + y * y <= dist * dist;
    },
    print: function(obj) {
        ctx.beginPath();
        ctx.arc(obj.x, obj.y, obj.r, 0, 2 * Math.PI);
        ctx.fillStyle = '#cccccc';
        ctx.fill();
    }

}
var G = Object.create(Grewer);
G.init();
var Ganim = function() {
    window.requestAnimationFrame(Ganim);

    ctx.fillStyle = '#fff';
    ctx.fillRect(0, 0, G.w, G.h);

    var length = G.arr.length;
    for (var i = 0; i < length; i++) {
        var o1 = G.arr[i]
        G.update(o1);
        G.print(o1);

        for (var j = i + 1; j < length; ++j) {

            var o2 = G.arr[j];
            if (G.checkDist(o1, o2, G.range)) {
                ctx.strokeStyle = '#cccccc';
                ctx.beginPath();
                ctx.moveTo(o1.x, o1.y);
                ctx.lineTo(o2.x, o2.y);
                ctx.stroke();
            }
        }

    }
}
G.arr.push({
    x: 1,
    y: 1,
    vx: 0,
    vy: 0,
    r: 1
})
document.addEventListener('mousemove', function(e) {
    G.arr[G.num].x = e.clientX;
    G.arr[G.num].y = e.clientY;
}, false)
Ganim();