准备工作

<canvas id="scratch" style="width: 800px; height: 500px;"></canvas>

window.onload = function () {
    var canvas = document.getElementById("scratch");

    // canvas dimensions 画布尺寸
    var width = parseInt(canvas.style.width);
    var height = parseInt(canvas.style.height);

    // retina 视网膜（显示屏）
    var dpr = window.devicePixelRatio || 1;    //设备像素比
    canvas.width = width*dpr;
    canvas.height = width*dpr;
    canvas.getContext("2d").scale(dpr, dpr);    //缩放

    /*
    * 【正文】才刚刚开始
    */
}

【正文】

// simulation 模拟器
var sim = new VerletJS(width, height, canvas);
sim.friction = 1;    //摩擦

// entities 实体
var segment = sim.lineSegments([new Vec2(20, 10)], 0.02);
var pin = segment.pin(0);

/*
*    这里可以添加更多【实体】
*/

// animation loop 动画循环
var loop = function() {
    sim.frame(16);
    sim.draw();
    requestAnimFrame(loop);
};

loop();

【实体】

var tire = sim.tire(new Vec(200, 50), 50, 30, 0.3, 0.9);

var min = Math.min(width, height)*0.5;
var segments = 20;
var cloth = sim.cloth(new Vec2(width/2, height/3), min, min, segments, 6, 0.9);