<canvas width="650px" height="500px" id="my-canvas">
  
</canvas>

let myCanvas = document.getElementById('my-canvas');

let ctx = myCanvas.getContext('2d');

ctx.strokeStyle = 'teal';
ctx.beginPath();
ctx.moveTo(80, 90);
ctx.lineTo(200, 400);
ctx.lineTo(400, 180);
ctx.closePath();

ctx.stroke();