Current script (thx th_pion for base)

github.com/thPion/Screeps-Nooby-Guide

src/role.harvester.js

@@ -0,0 +1,61 @@
+module.exports = {
+    // a function to run the logic for this role
+    /** @param {Creep} creep */
+    run: function(creep) {
+        // if creep is bringing energy to a structure but has no energy left
+        if (creep.memory.working == true && creep.carry.energy == 0) {
+            var time = creep.memory.ttl - creep.ticksToLive;
+            console.log(creep.name + " : " + creep.memory.role + " > " + time);
+
+            if(creep.ticksToLive < 100)
+                creep.suicide();
+            // switch state
+            creep.memory.ttl = creep.ticksToLive;
+            creep.memory.working = false;
+        }
+        // if creep is harvesting energy but is full
+        else if (creep.memory.working == false && creep.carry.energy == creep.carryCapacity) {
+            // switch state
+            creep.memory.working = true;
+        }
+
+        // if creep is supposed to transfer energy to a structure
+        if (creep.memory.working == true) {
+            // find closest spawn, extension or tower which is not full
+            var structure = creep.pos.findClosestByPath(FIND_MY_STRUCTURES, {
+                // the second argument for findClosestByPath is an object which takes
+                // a property called filter which can be a function
+                // we use the arrow operator to define it
+                filter: (s) => (s.structureType == STRUCTURE_SPAWN
+                    || s.structureType == STRUCTURE_EXTENSION
+                    || s.structureType == STRUCTURE_TOWER
+                    || s.structureType == STRUCTURE_LAB)
+                    && s.energy < s.energyCapacity
+            });
+
+            if (structure == undefined) {
+                structure = creep.room.storage;
+            }
+
+            // if we found one
+            if (structure != undefined) {
+                // try to transfer energy, if it is not in range
+                if (creep.transfer(structure, RESOURCE_ENERGY) == ERR_NOT_IN_RANGE) {
+                    // move towards it
+                    creep.moveTo(structure);
+                }
+            }
+
+            if (structure == undefined && (creep.ticksToLive < 50 || creep.carry.energy%50 != 0)) {
+                if (creep.upgradeController(creep.room.controller) == ERR_NOT_IN_RANGE) {
+                    // if not in range, move towards the controller
+                    creep.moveTo(creep.room.controller);
+                }
+            }
+        }
+        // if creep is supposed to harvest energy from source
+        else {
+            creep.getEnergy(false, true);
+        }
+    }
+};