Ll insertions

.eslintrc.json

@@ -0,0 +1,27 @@
+{
+    "env": {
+      "browser": true,
+      "node": true,
+      "commonjs": true,
+      "jest": true,
+      "es6": true
+    },
+    "globals": {
+      "err": true,
+      "req": true,
+      "res": true,
+      "next": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "rules": {
+      "no-console": "off",
+      "indent": [ "error", 2 ],
+      "quotes": ["error", "single", { "allowTemplateLiterals": true }],
+      "comma-dangle": ["error", "always-multiline"],
+      "semi": [ "error", "always" ]
+    }
+  }
+

README.md

@@ -1,6 +1,15 @@
-# Table of Contents
-[1- code challange class 2 array shift ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/3)
+# Singly Linked List
+## challange summary 
 
-[2- code challange class 3 array binary search ](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/pull/2)
+adding a new methods to the linked list 
+## Challenge description
+- append(value) which adds a new node with the given value to the end of the list
+- insertBefore(value, newVal) which add a new node with the given newValue immediately before the first value node
+- insertAfter(value, newVal) which add a new node with the given newValue immediately after the first value node
+
+## Approach & Efficiency
+i used  classes  and constructor format , while loop also i create a tests for it 
+## Solution
+
+![UML](https://github.com/Goorob-401-advanced-javascript/data-structures-and-algorithms/blob/ll-insertions/20200204_004602.jpg)
 
-[

challanges/ll-insertions/ll-insertion.js

@@ -0,0 +1,63 @@
+'use strict';
+
+class Node{
+  constructor(value){
+    this.value = value;
+    this.next = null;
+  }
+}
+class LinkedList {
+  constructor(){
+    this.head = null;
+  }
+  append (value){
+    let node  = new Node(value);
+    if(!this.head){
+      this.head = node;
+      return this;
+    }
+    let currentNode = this.head;
+    while(currentNode.next){
+      currentNode = currentNode.next;
+    }
+    currentNode.next = node;
+    return this;
+  }
+  insertBefore(value, newVal){
+    let node = new Node(newVal);
+    let currentNode = this.head;
+    let firstNode = null;
+
+    while(currentNode){
+      if(currentNode.value === value){
+        if(firstNode === null){
+          this.head = node;
+        }else{
+          firstNode.next = node;
+        }node.next = currentNode;
+        break;
+      }
+      firstNode = currentNode;
+      currentNode = currentNode.next;
+    }
+  }
+  insertAfter(value,newVal){
+    let newNode = new Node(newVal);
+    let currentNode = this.head;
+    let nextValue = null;
+    while(currentNode){
+      if(currentNode.value === value){
+        nextValue = currentNode.next;
+        currentNode.next = newNode;
+        newNode.next = nextValue;
+      }currentNode = currentNode.next;
+
+    }
+  }
+}
+// let ll =new LinkedList();
+// list.append('1');
+// list.append('2');
+// list.insertBefore('1','3');
+// console.log(ll);
+module.exports = LinkedList;

challanges/ll-insertions/ll-insertion.test.js

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+const LinkedList = require('./ll-insertion.js');
+
+describe('LL Module',()=>{
+  it ('constructor',()=>{
+    let list = new LinkedList();
+    expect(list.head).toBeNull();
+
+  });
+
+  it('append()',()=>{
+    let ll = new LinkedList();
+
+    ll.append('1');
+    expect(ll.head.value).toEqual('1');
+    expect(ll.head.value.next).toBeAnObject;
+  });
+
+  it('insertBefore()',()=>{
+    let ll = new LinkedList();
+    let initVal = '1';
+    ll.append(initVal);
+    ll.insertBefore(initVal,'2');
+    expect(ll.head.value).toEqual('2');
+  });
+
+  it('insertAfter()',()=>{
+    let ll = new LinkedList();
+    let initVal = '1';
+    ll.append(initVal);
+    ll.insertAfter(initVal,'2');
+    expect(ll.head.value).toEqual('1');
+    expect(ll.head.value.next).toBeAnObject;
+  });
+
+});