Refactor: JavaScript/lib (#68)

Creates a new directory `lib` within the `JavaScript` solutions directory to store re-usable functions and classes.

The general pattern to follow would be: `JavaScript/lib/{{ github_handle }}/{{ category }}`

So for the case of "Chapter 2: Linked Lists", I would add a new file `JavaScript/lib/avc278/linkedlist.js`.

Author: avc278

JavaScript/chapter02/p01_remove_dups/avc278.js

@@ -2,33 +2,10 @@
 // Follow Up: How would you solve this problem if a temporary buffer is not allowed?
 
 const assert = require("assert");
-
-class LinkedListNode {
-  constructor(val, next) {
-    this.val = val === undefined ? null : val;
-    this.next = next === undefined ? null : next;
-  }
-}
-
-const arrayToLinkedList = (arr) => {
-  let tail = null;
-  for (let i = arr.length - 1; i >= 0; i--) {
-    tail = new LinkedListNode(arr[i], tail);
-  }
-  return tail;
-};
-
-const compareLinkedLists = (A, B) => {
-  if (!A && !B) return true;
-
-  while (A !== null && B !== null) {
-    if (A.val !== B.val) return false;
-    A = A.next;
-    B = B.next;
-  }
-
-  return !A && !B;
-};
+const {
+  arrayToLinkedList,
+  compareLinkedLists,
+} = require("../../lib/avc278/linkedlist");
 
 /**
  * Removes duplicates from a linked list
@@ -47,7 +24,11 @@ const removeDups1 = (list) => {
   const seen = new Set();
   let currNode = list;
   seen.add(currNode.val);
-  for (let nextNode = currNode.next; nextNode.next !== null; nextNode = nextNode.next) {
+  for (
+    let nextNode = currNode.next;
+    nextNode.next !== null;
+    nextNode = nextNode.next
+  ) {
     if (seen.has(nextNode.val)) continue;
 
     seen.add(nextNode.val);
@@ -109,15 +90,5 @@ removeDups.forEach((removeDup) => {
       removeDup(ll1);
       assert.ok(compareLinkedLists(ll1, expectedLL1));
     });
-    it("should return false when comparing unequal linked lists", () => {
-      assert.ok(
-        !compareLinkedLists(arrayToLinkedList([]), arrayToLinkedList(["hi!"]))
-      );
-    });
-    it("should return false when comparing another pair of unequal linked lists", () => {
-      assert.ok(
-        !compareLinkedLists(arrayToLinkedList([1, 2]), arrayToLinkedList([1]))
-      );
-    });
   });
 });

JavaScript/chapter02/p02_return_kth_to_last/avc278.js

@@ -1,21 +1,9 @@
 // Return Kth to Last: Implement an algorithm to find the kth to last element of a singly linked list.
 
 const assert = require("assert");
-
-class LinkedListNode {
-  constructor(val, next) {
-    this.val = val === undefined ? null : val;
-    this.next = next === undefined ? null : next;
-  }
-}
-
-const arrayToLinkedList = (arr) => {
-  let tail = null;
-  for (let i = arr.length - 1; i >= 0; i--) {
-    tail = new LinkedListNode(arr[i], tail);
-  }
-  return tail;
-};
+const {
+  arrayToLinkedList,
+} = require("../../lib/avc278/linkedlist");
 
 /**
  * Returns the kth to last node in a linked list

JavaScript/chapter02/p03_delete_middle_node/avc278.js

@@ -5,32 +5,11 @@
 // Result: nothing is returned, but the new linked list looks like a => b => d => e => f
 
 const assert = require("assert");
+const {
+  arrayToLinkedList,
+  compareLinkedLists,
+} = require("../../lib/avc278/linkedlist");
 
-class LinkedListNode {
-  constructor(val, next) {
-    this.val = val === undefined ? null : val;
-    this.next = next === undefined ? null : next;
-  }
-}
-
-const arrayToLinkedList = (arr) => {
-  let tail = null;
-  for (let i = arr.length - 1; i >= 0; i--) {
-    tail = new LinkedListNode(arr[i], tail);
-  }
-  return tail;
-};
-
-const compareLinkedLists = (A, B) => {
-  if (!A && !B) return true;
-
-  while (A !== null && B !== null) {
-    if (A.val !== B.val) return false;
-    A = A.next;
-    B = B.next;
-  }
-  return !A && !B;
-};
 /**
  * Deletes an inputted node somewhere in the middle of the linked list
  * @param  {LinkedListNode} node input node to be removed

JavaScript/lib/avc278/linkedlist.js

@@ -0,0 +1,43 @@
+const assert = require("assert");
+
+class LinkedListNode {
+  constructor(val, next) {
+    this.val = val === undefined ? null : val;
+    this.next = next === undefined ? null : next;
+  }
+}
+
+const arrayToLinkedList = (arr) => {
+  let tail = null;
+  for (let i = arr.length - 1; i >= 0; i--) {
+    tail = new LinkedListNode(arr[i], tail);
+  }
+  return tail;
+};
+
+const compareLinkedLists = (A, B) => {
+  if (!A && !B) return true;
+
+  while (A !== null && B !== null) {
+    if (A.val !== B.val) return false;
+    A = A.next;
+    B = B.next;
+  }
+
+  return !A && !B;
+};
+
+describe(module.filename, () => {
+  it("should return false when comparing unequal linked lists", () => {
+    assert.ok(
+      !compareLinkedLists(arrayToLinkedList([]), arrayToLinkedList(["hi!"]))
+    );
+  });
+  it("should return false when comparing another pair of unequal linked lists", () => {
+    assert.ok(
+      !compareLinkedLists(arrayToLinkedList([1, 2]), arrayToLinkedList([1]))
+    );
+  });
+});
+
+module.exports = { arrayToLinkedList, compareLinkedLists };