An algorithm used to handle unconnected regions of a map.

floodfill.js

// this variable will be used to store the various unconnected caverns
var caverns = [];

// begin looping through the map
for(var x = 1; x<this.size.x; x++) {
    for(var y = 1; y<this.size.y; y++) {
        var cavern = [];
        var totalCavern = [];
        
        if(this.data[x][y].type != "dirty floor") {
            // we've already been over this tile or it is already part of a cavern, 
            // no need to check it
            continue;
        }
        
        cavern.push(this.data[x][y]);
        totalCavern.push(this.data[x][y]);
        
        while(cavern.length > 0) {
            var n = cavern.pop();
            
            if(n.type == "dirty floor") {
                // set a flag on the tile indicating it has already been checked
                n.setType("floor");
                
                for(var i = 0; i<8; i++) {
                    var curTile = this.data[n.position.x + x_array[i]][n.position.y + y_array[i]];
                    if(curTile.type == "dirty floor") {
                        cavern.push(curTile);
                        totalCavern.push(curTile);
                    }
                }
            }
        }
        
        // add this cavern
        caverns.push(totalCavern);
        
        // sort the caverns
        caverns.sort(function(a, b) {
            return(b.length - a.length);
        });
    }
}

// remove the largest cavern, as it is the main cavern
caverns.shift();

// now that we've got the unconnected caverns, change their tile type
if(caverns.length > 0) {
    for(var i = 0; i<caverns.length; i++) {
        for(var j = 0; j<caverns[i].length; j++) {
            caverns[i][j].setType("wall");
        }
    }
}