Prototype Pattern
– Using prototypes to create classes, all instances of that class will the same functions.
– Can’t have private utility functions. All properties and functionalities can be seen by caller.
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"use strict"; var StepEnum = Object.freeze({NEXT: "step next", PREV: "step previous"}); function ListNode(newData, newPrev, newNext) { // this = {} if (new.target === undefined) { console.log('You didnt use new. Giving you a new Node Object'); return new Node(); } // public properties this.data = newData; this.next = newNext; this.prev = newPrev; // public functions this.clean = function() { this.data = null; this.next = null; this.prev = null; } this.display = function() { console.log("[" + this.data + "]") } // return this } // List Node function List(newName) { this.head = null; this.tail = null; this.now = null; this.listName = newName; // private // O(1) this.removeLastNode = function(data, ref) { if (this.dataMatches(data.toUpperCase(), ref.data.toUpperCase())) { if (this.head === this.tail) { this.head = this.head.next = this.head.prev = null; this.tail = this.tail.next = this.tail.prev = null; ref.clean(); return true; } } return false; } // private this.removeNodeAtHead = function(ref) { if (ref === this.head) { var temp = ref; ref.next.prev = this.tail; ref.prev.next = ref.next; this.head = ref.next; temp.clean(); return true; } return false; } // private // O(1) this.removeNodeAtTail = function(ref) { if (ref === this.tail) { var temp = ref; ref.next.prev = ref.prev; ref.prev.next = ref.next; this.tail = ref.prev; temp.clean(); return true; } return false; } // private // O(1) this.removeNodeInBetween = function(ref) { if ((ref !== this.tail) && (ref !== this.head)) { ref.next.prev = ref.prev; ref.prev.next = ref.next; ref.clean(); return true; } return false; } } List.prototype.about = function() { console.log(`Circular list (${this.listName}) with nodes that reference next and previous. Ricky Tsao 2018`); } List.prototype.current = function() { return this.now; } List.prototype.setCurrentToHead = function() { this.now = this.head; return this.now; } List.prototype.setCurrentToTail = function() { this.now = this.tail; return this.now }; List.prototype.step = function(steps, StepEnum) { if(!isNaN(steps) && steps > 0) { while (steps > 0) { this.now = (StepEnum.NEXT) ? this.now.next : this.now.prev; steps--; } } } List.prototype.isEmpty = function() { return (!this.head && !this.tail); } List.prototype.insert = function(data) { console.log("PROTOTYPE - Inserting data: " + data); try { if (!this.isString(data)) throw "Data Must be a String"; if (this.isEmpty()) { this.head = new ListNode(data, null, null); this.tail = this.head; } else { this.tail = new ListNode(data, this.tail, this.head); this.tail.prev.next = this.tail; this.head.prev = this.tail; } this.now = this.tail; } catch(err) { console.log("\n------ ERROR ------"); console.log("description: data not entered"); console.log("reason: " + err); console.log("===================\n\n") } } // Notice that in our prototype, we can use private functions from List // public // O(n) List.prototype.remove = function(data) { if (this.isEmpty()) { console.log("Nothing to remove because list is empty"); return; } try { var traversal = this.head; if (this.removeLastNode(data, traversal)) { return;} do { if (this.dataMatches(data.toUpperCase(), traversal.data.toUpperCase())) { if (this.removeNodeAtHead(traversal)) return; if (this.removeNodeAtTail(traversal)) return; if (this.removeNodeInBetween(traversal)) return; } traversal = traversal.next; } while (traversal != this.head); } catch(error) { console.log("Warning: "+ error); } }; List.prototype.dataMatches = function(data1, data2) { return (data1.toUpperCase() === data2.toUpperCase()); } List.prototype.isString = function(data) { return ((typeof data) === 'string'); } List.prototype.display = function() { console.log("PROTOTYPE - display CircularList: " + this.listName) if (this.isEmpty()) { console.log("-- LIST (" + this.listName + ") IS EMPTY --"); return; } var traversal = this.head; console.log("-----" + this.listName + "-----"); do { traversal.display(); traversal = traversal.next; } while (traversal !== this.head && traversal != null); console.log("===============") } var metro = new List("metro"); metro.about(); metro.insert("Hou Hai"); metro.insert("Keyuan"); metro.insert("Window of the World"); metro.display(); metro.remove("Window of the World"); metro.display(); metro.remove("Hou Hai"); metro.display(); metro.remove("Window of the World"); metro.display(); metro.remove("Shui wan"); metro.display(); metro.remove("Keyuan"); metro.display(); |
Constructor Pattern with scoped private variables
By using scoped variables, we can have privacy, and can create get/set functionalities for public access.
However, not very practical as I will need to create get/set functions for all the private variables.
Then, using them in my functions can be awkward as assigning references must be dealt with using set functions.
And being assigned, we’ll have to call the get functions.
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class CircularList { constructor(listName) { console.log("Constructing CircularList " + listName); // https://stackoverflow.com/questions/22156326/private-properties-in-javascript-es6-classes // create private variable // assign it to incoming parameter var _name = listName; // setting new name this.setName = function(listName) { _name = listName;} // getting the new name this.getName = function() { return _name; } // private member variables var _head = null; this.setHead = function(newHead) {_head = newHead;} this.getHead = function() {return _head;} var _tail = null; this.setTail = function(newTail) {_tail = newTail;} this.getTail = function() {return _tail;} var _now = null; this.setNow = function(newNow) {_now=newNow;} this.getNow = function() {return _now;} console.log("Finished constructing CircularList") } // constructor isString(data) { return ((typeof data) === 'string'); } isEmpty() { return (this.getHead() == null && this.getTail() == null); } insert(data) { console.log("CircularList - Inserting data: " + data); try { if (!this.isString(data)) throw "Data Must be a String"; if (this.isEmpty()) { this.setHead(new ListNode(data, null, null)); this.setTail(this.getHead()); } else { this.setTail(new ListNode(data, this.getTail(), this.getHead())); this.getTail().prev.next = this.getTail(); this.getHead().prev = this.getTail(); } this.setNow(this.getTail()); } catch(err) { console.log("\n------ ERROR ------"); console.log("description: data not entered"); console.log("reason: " + err); console.log("===================\n\n") } } print() { if (this.getHead() === null) { console.log("-- LIST IS EMPTY --"); return; } var traversal = this.getHead(); do { traversal.display(); traversal = traversal.next; } while (traversal !== this.getHead() && traversal != null); } } let a = new CircularList("rickylist") a.insert("ricky"); a.insert("bob"); a.insert("claire"); a.print(); |