<html>
<head>
<meta charset="utf-8">
<title>Mocha Tests</title>
<link href="https://unpkg.com/mocha@5.2.0/mocha.css" rel="stylesheet" />
</head>
<body>
<div id="mocha"></div>
<script src="https://unpkg.com/chai/chai.js"></script>
<script src="https://unpkg.com/mocha@5.2.0/mocha.js"></script>
<div></div>
</body>
</html>class Node {
constructor(data){
this.data = data;
this.prev = null;
this.next = null;
}
}
class DoublyLinkedList{
constructor(){
this.head = null;
this.tail = null;
this.length = 0;
}
push(data){
const node = new Node(data);
if(!this.head){
this.head = node;
this.tail = node;
}else{
node.prev = this.tail;
this.tail.next = node;
this.tail = node;
}
this.length++;
}
pop(){
if(!this.head) return null
// tail is the last node so that we take the
// prev property from the tail
const prevNode = this.tail.prev
if(prevNode){
prevNode.next = null;
this.tail = prevNode; // updating the tail
}else{
// if prev property is null
// it means there is only single node
this.head = null;
this.tail = null;
}
this.length--; //decrement the length
}
insertBeginning(data){
// new node is created
const node = new Node(data);
// if there is no nodes
if(!this.head) {
this.head = node;
this.tail = node;
}else{
// update the head.prev to the new node
// take the new node.next property and link it to the
// head property
this.head.prev = node
node.next = this.head;
this.head = node;
}
// increment the length
this.length++;
}
removeFirst(){
if(!this.head) return null
const node = this.head.next;
if(node){
node.prev = null
this.head = node
}else{
this.head = null
this.tail = null
}
this.length--;
}
}
mocha.setup('bdd');
var assert = chai.assert;
describe('Doubly Linked list',()=>{
it("should add the new node at the end",()=>{
const list = new DoublyLinkedList();
list.push(1)
list.push(2)
list.push(3)
list.push(4)
assert.equal(4,list.length)
})
it("should remove the node at the end",()=>{
const list = new DoublyLinkedList();
list.push("A")
list.push("B")
list.push("C")
list.push("D")
list.pop();
list.pop();
assert.equal(2,list.length)
assert.equal("B",list.tail.data)
})
it("should insert the new node at the beginning",()=>{
const list = new DoublyLinkedList();
list.push("C")
list.push("D")
list.insertBeginning("B");
list.insertBeginning("A");
assert.equal(4,list.length);
assert.equal("A",list.head.data)
})
it("should remove the node at the beginning",()=>{
const list = new DoublyLinkedList();
list.push("C")
list.push("D")
list.insertBeginning("B");
list.insertBeginning("A");
list.removeFirst()
assert.equal(3,list.length);
assert.equal("B",list.head.data)
})
})
mocha.run()
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