如何禁用画布缩放

canvas {
  touch-action: manipulation;
}

var canvas = document.getElementById('myCanvas');

canvas.addEventListener('touchstart', function(e) {
  if (e.touches.length > 1) {
    e.preventDefault();
  }
});

canvas.addEventListener('touchmove', function(e) {
  if (e.touches.length > 1) {
    e.preventDefault();
  }
});

canvas.addEventListener('gesturestart', function(e) {
  e.preventDefault();
});

<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">