小编tem*_*emp的帖子

document.getElementById("canvas")
        .addEventListener("click", setPath, false);

function setPath() {
  if (check) {
    document.getElementById("canvas").
        addEventListener("mousemove", mouseOverPath, false);
  } else {
    document.getElementById("canvas").
        removeEventListener("mousemove", mouseOverPath, false);
  }

  function mouseOverPath(event) {
    drawLine.x = event.clientX;
    drawLine.y = event.clientY;
    drawLine.draw();
  }

}

document.getElementById("canvas").
        addEventListener("click", () => {
  if (check == true) {
    check = false;
  } else if (check == false) {
    check = true;
  }
}, false);

<canvas id="canvas" height="200" width="200" style="border:1px solid black;">