Canvas实现弧线时钟

createClock("#myclock",0,0.5);
function createClock(selector,n,p_r){
    var weeks    =["Sun","Mon","Tue","Wed","Thu","Fri","Sat"];
    var p_b        =0.11;
    var p_d        =0.4;
    var n_c        ="rgba(255,150,0,1)";
    var canv    =document.createElement("canvas");
    var c        =canv.getContext("2d");
    var p        =document.querySelectorAll(selector)[n];
    p.appendChild(canv);
    
    canv.style.display    ="block";

    var r,b,l;
    function resizing(){
        r             = p_r * p.clientWidth;
        canv.width        =canv.height=2*r;
        b                =p_b*r;
        l                =r-(3+2*p_d)*b;
        c.lineWidth        =b;
        c.lineCap        ="round";
        c.strokeStyle    =n_c;
    }
    resizing();
    window.addEventListener("resize",resizing);
    
    function fraps(){
        var t=new Date();
        var ds=t.getFullYear()+"/"+ct(t.getMonth()+1)+"/"+ct(t.getDate());
        var ws=weeks[t.getDay()];
        var hs=ct(t.getHours())+":"+ct(t.getMinutes());
        var ss=ct(t.getSeconds());
        var sn=t.getSeconds()+0.001*t.getMilliseconds();
        var mn=t.getMinutes()+sn/60;
        var hn=t.getHours()+mn/60;
        if(hn>12)hn-=12;
        
        c.clearRect(0,0,2*r,2*r);
        
        var phsf=0.65;
        var phsx=1.3;
        var phsy=0.38;
        var hs_c="red";
        c.font=phsf*l+"px Arial bold";
        c.fillStyle=hs_c;
        c.fillText(hs,r-phsx*phsf*l,r+phsy*phsf*l);
        /*
        c.font=0.3*l+"px Arial bold";
        c.fillStyle="red";
        c.fillText(ds,r-0.5*l,r);
        c.font=0.3*l+"px Arial bold";
        c.fillStyle="red";
        c.fillText(ws,r-0.5*l,r);
        c.font=0.3*l+"px Arial bold";
        c.fillStyle="red";
        c.fillText(ss,r-0.5*l,r);*/
        
        c.beginPath();
        c.arc(r,r,r-0.5*b,-0.5*Math.PI,(sn/30-0.5)*Math.PI);
        c.stroke();
        c.beginPath();
        c.arc(r,r,r-(1.5+p_d)*b,-0.5*Math.PI,(mn/30-0.5)*Math.PI);
        c.stroke();
        c.beginPath();
        c.arc(r,r,r-(2.5+2*p_d)*b,-0.5*Math.PI,(hn/6-0.5)*Math.PI);
        c.stroke();
    }
    function ct(i){
        if (i<10)i="0"+i;
        return i;
    }
}