运行效果：
<!DOCTYPE html><html><head></head><body><canvas id="drawing" width="800" height="600">A drawing of someing!</canvas> <script type="text/javascript">var drawing = document.getElementById('drawing');if(drawing.getContext) {//绘制奥运五环，画圆var context = drawing.getContext('2d'); context.lineWidth = 7; context.strokeStyle = '#0180C3'; context.beginPath(); context.arc(70, 70, 40, 0, 2*Math.PI, false); context.stroke(); context.strokeStyle = '#000'; context.beginPath(); context.arc(160, 70, 40, 0, 2*Math.PI, false); context.stroke(); context.strokeStyle = '#BF0628'; context.beginPath(); context.arc(250, 70, 40, 0, 2*Math.PI, false); context.stroke(); context.strokeStyle = '#EBC41F'; context.beginPath(); context.arc(115, 110, 40, 0, 2*Math.PI, false); context.stroke(); context.strokeStyle = '#198E4A'; context.beginPath(); context.arc(205, 110, 40, 0, 2*Math.PI, false); context.stroke();//环环相扣，画弧（实现相关圆弧的覆盖）context.strokeStyle = '#0180C3'; context.beginPath(); context.arc(70, 70, 40, 1.9*Math.PI, 2.1*Math.PI, false); context.stroke(); context.strokeStyle = '#000'; context.beginPath(); context.arc(160, 70, 40, 1.9*Math.PI, 2.1*Math.PI, false); context.stroke(); context.beginPath(); context.arc(160, 70, 40, 0.5*Math.PI, 0.7*Math.PI, false); context.stroke(); context.strokeStyle = '#BF0628'; context.beginPath(); context.arc(250, 70, 40, 0.5*Math.PI, 0.7*Math.PI, false); context.stroke(); }</script></body></html>
