targets=Game.rooms[xroom].find(FIND_STRUCTURES, {filter: {structureType: STRUCTURE_WALL}});
Sometimes, the key/value pair for hits is not included in the object returned.
console.log(target[i].id+":"+target[i].hits);
[10:23:02 PM][shard3]6091683b24e3167444cb0db4:100001
[10:23:02 PM][shard3]6091683eae27db4155ac302e:100001
[10:23:02 PM][shard3]609ab7c76988d8375e4595b6:undefined
[10:23:02 PM][shard3]609ab7c76988d8375e4595b7:undefined