canvas
<!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1"> <title></title> <style type="text/css"> canvas { border: 1px solid #333; } </style> </head> <body> <!-- canvas画布的大小,不能用css来调整,用属性来调整 --> <canvas id="canvas" width="600" height="400"></canvas> </body> <script type="text/javascript"> //获取画布 let canvas = document.getElementById("canvas"); //获取上下文 let ctx = canvas.getContext("2d"); ctx.translate(300,200) //绘制大圆 ctx.arc(0,0,200,0,Math.PI*2,false) ctx.stroke() //绘制上面的线 ctx.beginPath() ctx.moveTo(0,-200) ctx.lineTo(0,0) ctx.stroke() //绘制右边的线 ctx.beginPath() ctx.moveTo(0,0) let x=200*Math.cos(30*(Math.PI/180)) let y=200*Math.sin(30*(Math.PI/180)) ctx.lineTo(x,y) ctx.stroke() //绘制左边的线 ctx.beginPath() ctx.moveTo(0,0) let x2=200*Math.cos(150*(Math.PI/180)) let y2=200*Math.sin(150*(Math.PI/180)) ctx.lineTo(x2,y2) ctx.stroke() </script> </html>