<canvas id="canvas" width="500" height="500"></canvas>
    代碼如下:
    var canvas=document.getElementById("canvas");
    var cxt=canvas.getContext("2d");
    cxt.beginPath();
    cxt.moveTo(250,50);
    cxt.lineTo(200,200);
    cxt.lineTo(300,300);
    cxt.closePath();//填充或閉合 需要先閉合路徑才能畫
    //空心三角形
    cxt.strokeStyle="red";
    cxt.stroke();
    //實心三角形
    cxt.beginPath();
    cxt.moveTo(350,50);
    cxt.lineTo(300,200);
    cxt.lineTo(400,300);
    cxt.closePath();
    cxt.fill();