Spatial Hash in Javascript, for 2D.

var SpatialHash = function(cellSize) {
 this.idx = {};
 this.cellSize = cellSize;
}  
 
SpatialHash.prototype.insert = function(x, y, obj) {
 var cell = [];
 var keys = this.keys(x,y);
 for(var i in keys) {
  var key = keys[i];
  if(key in this.idx) {
   cell = this.idx[key];
  } else {
   this.idx[key] = cell;   
  }
  if(cell.indexOf(obj) == -1)
   cell.push(obj);
 }
}

SpatialHash.prototype.query = function(x, y) {
 var key = this.key(x, y);
 if(this.idx[key] != undefined)
  return this.idx[key];
 return [];
}

SpatialHash.prototype.keys = function (x, y)  {
 var o = this.cellSize / 2;
 return [this.key(x-o, y+0), 
   this.key(x-0, y+0),
   this.key(x+o, y+0),
   this.key(x-o, y+o),
   this.key(x-0, y+o),
   this.key(x+o, y+o),
   this.key(x-o, y-o),
   this.key(x-0, y-o),
   this.key(x+o, y-o)];
}

SpatialHash.prototype.key = function(x, y) {
 var cellSize = this.cellSize;
 x = Math.floor(x/cellSize)*cellSize;
 y = Math.floor(y/cellSize)*cellSize;
 return x.toString() + ":" + y.toString();
}