Current script (thx th_pion for base)

github.com/thPion/Screeps-Nooby-Guide

src/prototype.tower.js

@@ -0,0 +1,18 @@
+StructureTower.prototype.defend =
+    function () {
+        // find closes hostile creep
+        var target = this.pos.findClosestByRange(FIND_HOSTILE_CREEPS);
+        // if one is found...
+        if (target != undefined) {
+            // ...FIRE!
+            this.attack(target);
+        }
+        
+        var closestDamagedStructure = this.pos.findClosestByRange(FIND_STRUCTURES, {
+            filter: (structure) => structure.hits < structure.hitsMax
+        });
+        
+        if(closestDamagedStructure) {
+            this.repair(closestDamagedStructure);
+        }
+    };