for (var i = 0; i < (minJumps + (Math.random() * (maxJumps - minJumps))); i++) {
  dX = jump();
  dY = jump();
  window.moveBy(dX, dY);
  totalX -= dX;
  totalY -= dY;
}

Since we have no way of knowing the window's initial position, we must keep track of how much we moved it in each direction. The totalX and totalY variables hold the window's position in relation to its initial position, before the quake began. When the quake is over, the window is moved back to its origianl position:

window.moveBy(totalX, totalY);
totalX = 0;
totalY = 0;

The winShake() function is then called again after a random pause:

quakeID = setTimeout("winShake()", Math.ceil(Math.random() *
  (maxBetweenQuakes - minBetweenQuakes)) + minBetweenQuakes);

The script generates a series of earthquakes. It begins when the page loads (window.onload).

See the full script in Tutorial 1, Working with Windows.

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