旋转的辐射Logo

var canvas = document.getelementbyid("mycanvas"); 
var context = canvas.getcontext("2d"); 
var startp = [0 , 0.67 , 1.34 ]; 
var endp = [0.3 , 0.97 , 1.64]; 
var n = 0.01; 
var animate; 
window.onload = initpage; 
 
function initpage() { 
    var speed = document.getelementsbytagname("select")[0].value; 
    window.clearinterval(animate); 
    animate = setinterval("show()",speed); 
} 
 
function show() { 
    context.clearrect(0,0,500,500); 
    for(var i = 0 ; i<3 ; i++) { 
    startp[i] += n; 
    endp[i] += n; 
    if(startp[i] == 2) { 
        startp[i] = 0; 
    } 
    if(endp[i] == 2) { 
        endp[i] = 0; 
    } 
    } 
    context.beginpath(); 
    context.rect(0,0,500,500); 
    context.linewidth = 1; 
    context.fillstyle = "#f2ca07"; 
    context.fill(); 
    context.stroke(); 
 
    context.beginpath(); 
    context.arc(250, 250, 10, 0, 2 * math.pi, false); 
    context.linewidth = 1; 
    context.fillstyle = "#333"; 
    context.fill(); 
    context.stroke(); 
 
    context.beginpath(); 
    context.arc(250, 250, 100, startp[0] * math.pi, endp[0] * math.pi, false); 
    context.linewidth = 160; 
    context.strokestyle = "#333"; 
    context.stroke(); 
 
    context.beginpath(); 
    context.arc(250, 250, 100, startp[1] * math.pi, endp[1] * math.pi, false); 
    context.linewidth = 160; 
    context.strokestyle = "#333"; 
    context.stroke(); 
 
    context.beginpath(); 
    context.arc(250, 250, 100, startp[2] * math.pi, endp[2] * math.pi, false); 
    context.linewidth = 160; 
    context.strokestyle = "#333"; 
    context.stroke(); 
} 

demo

摘自 简生的代码备忘录