1. Review of the previous article:
In the last article, we implemented a list class, added some properties, and implemented many methods. In this article, we will use lists to implement a book borrowing query system with you. You need to use the list class List() written in JavaScript data structure and algorithm - List Detailed Explanation (above ).
If you want to view the code description of the List() class, please refer to the previous explanation of my list. Here only the source code of List is given for the next writing call:
function List() {
this.listSize = 0
this.pos = 0
this.dataStore = [] // initialize an empty array to hold list elements
this.clear = clear
this.find = find
this.toString = toString
this.insert = insert
this.append = append
this.remove = remove
this.front = front
this.end = end
this.prev = prev
this.next = next
this.hasNext = hasNext
this.hasPrev = hasPrev
this.length = length
this.currPos = currPos
this.moveTo = moveTo
this.getElement = getElement
this.contains = contains
}
function append(element) {
this.dataStore[this.listSize++] = element
}
function find(element) {
for (var i = 0; i < this.dataStore.length; i++) {
if (this.dataStore[i] == element) {
return i
}
}
return -1
}
function remove(element) {
var foundAt = this.find(element)
if (foundAt > -1) {
this.dataStore.splice(foundAt, 1)
this.listSize--
return true
}
return false
}
function length() {
return this.listSize
}
function toString() {
return this.dataStore.toString()
}
function insert(element, after) {
var insertPos = this.find(after)
if (insertPos > -1) {
this.dataStore.splice(insertPos + 1, 0, element)
this.liseSize++
return true
}
return false
}
function clear() {
delete this.dataStore
this.dataStore.length = 0
this.listSize = 0
this.pos = 0
}
function contains(element) {
for (var i = 0; i < this.dataStore.length; i++) {
return true
}
return false
}
// loop through the list
function front() {
this.pos = 0
}
function end() {
this.pos = this.listSize - 1
}
function prev() {
this.pos--
}
function next() {
if (this.pos < this.listSize) {
this.pos++
}
}
function currPos() {
return this.pos
}
function moveTo(position) {
this.pos = position
}
function hasNext() {
return this.pos < this.listSize
}
function hasPrev() {
return this.pos >= 0
}
function getElement() {
return this.dataStore[this.pos]
}
2. Implement a book borrowing query system based on Nodejs using lists
Create a new List folder, which contains a book.txt (for storing books) and a book.js for writing js (please load the List() related code implemented in the previous article first).
2.1 Reading book files
// Created by xiaoqiang on 05/04/2018.
var fs = require('fs')
function readBooks('book.txt') {
var data = fs.readFileSync(file)
var dataArray = data.toString (). split ('\ n')
for (var i = 0; i < dataArray.length; i++) {
dataArray [i] = dataArray [i] .trim ()
}
return dataArray
}
During the writing process, console.log(readBooks('book.txt')) can be added outside the function to facilitate testing, enter the current folder, use the command node book.js , and see the following results to prove that the node environment is ok && function writing question:
2.2 Save books to list
As we said at the beginning, we wrote a List() class in the previous article. Next, we create a book list object through this class, and add elements to the dataStore property in the list object.
function saveBooksToList(file) {
var booksArray = readBooks (file)
for (var i = 0; i < booksArray.length; i++) {
bookList.append(booksArray[i])
}
}
2.3 Display list information
function displayList(list) {
for (list.front(); list.currPos() < list.length(); list.next()) {
console.log(list.getElement())
}
}
test:
var bookList = new List()
saveBooksToList('book.txt')
displayList(bookList)
operation result:
2.4 Create a borrower method
This method is used to save which books were borrowed by which person.
// borrower information
function borrower(name, book) {
this.name = name
his.book = book
}
2.5 Implement the borrowing method
// borrow book
function borrowBook(name, book, bookList, borrowerList) {
if (bookList.contains(book)) {
var b = new borrower(name, book)
borrowerList.append(b)
bookList.remove(book)
console.log(name + 'borrowing book' + book + 'success!!!')
} else {
console.log('The book has been borrowed!!!')
}
}
Explanation: The meanings of the four parameters are: the name of the borrower, the book to be borrowed, the list of books, and the list of borrowers; first check whether the book exists, if it exists, save the book and the borrower information to the borrower list, if the information does not exist, prompt error message.
2.6 Final result test
// book list object
var bookList = new List()
// borrower list object
var borrowerList = new List()
// save book to list
saveBooksToList('book.txt')
console.log('------------Currently available books-------------------')
// display book information
displayList(bookList)
console.log('-----------------Start borrowing books-------------------')
// borrow book
borrowBook('xgq', 'Nodejs详解', bookList, borrowerList)
console.log('-----------------borrowing information-------------------')
// Display the list of borrowers
displayList(borrowerList)
console.log('-----------------Remaining books that can be borrowed---------------')
// List of books left after borrowing
displayList(bookList)
result:
2.7 The complete code of book.js (integration of the previous part):
// Created by xiaoqiang on 05/04/2018.
var fs = require('fs')
var readline = require('readline')
// JavaScript data structure and algorithm - detailed list (on)
function List() {
this.listSize = 0
this.pos = 0
this.dataStore = [] // initialize an empty array to hold list elements
this.clear = clear
this.find = find
this.toString = toString
this.insert = insert
this.append = append
this.remove = remove
this.front = front
this.end = end
this.prev = prev
this.next = next
this.hasNext = hasNext
this.hasPrev = hasPrev
this.length = length
this.currPos = currPos
this.moveTo = moveTo
this.getElement = getElement
this.contains = contains
}
function append(element) {
this.dataStore[this.listSize++] = element
}
function find(element) {
for (var i = 0; i < this.dataStore.length; i++) {
if (this.dataStore[i] == element) {
return i
}
}
return -1
}
function remove(element) {
var foundAt = this.find(element)
if (foundAt > -1) {
this.dataStore.splice(foundAt, 1)
this.listSize--
return true
}
return false
}
function length() {
return this.listSize
}
function toString() {
return this.dataStore.toString()
}
function insert(element, after) {
var insertPos = this.find(after)
if (insertPos > -1) {
this.dataStore.splice(insertPos + 1, 0, element)
this.liseSize++
return true
}
return false
}
function clear() {
delete this.dataStore
this.dataStore.length = 0
this.listSize = 0
this.pos = 0
}
function contains(element) {
for (var i = 0; i < this.dataStore.length; i++) {
return true
}
return false
}
// traverse the list method
function front() {
this.pos = 0
}
function end() {
this.pos = this.listSize - 1
}
function prev() {
this.pos--
}
function next() {
if (this.pos < this.listSize) {
this.pos++
}
}
function currPos() {
return this.pos
}
function moveTo(position) {
this.pos = position
}
function hasNext() {
return this.pos < this.listSize
}
function hasPrev() {
return this.pos >= 0
}
function getElement() {
return this.dataStore[this.pos]
}
// read the book file
function readBooks (file) {
var data = fs.readFileSync(file)
var dataArray = data.toString (). split ('\ n')
for (var i = 0; i < dataArray.length; i++) {
dataArray [i] = dataArray [i] .trim ()
}
return dataArray
}
// save book to list
function saveBooksToList(file) {
var booksArray = readBooks (file)
for (var i = 0; i < booksArray.length; i++) {
bookList.append(booksArray[i])
}
}
// display list information
function displayList(list) {
for (list.front(); list.currPos() < list.length(); list.next()) {
console.log(list.getElement())
}
}
// borrower information
function borrower(name, book) {
this.name = name
this.book = book
}
// borrow book
function borrowBook(name, book, bookList, borrowerList) {
if (bookList.contains(book)) {
var b = new borrower(name, book)
borrowerList.append(b)
bookList.remove(book)
console.log(name + 'borrowing book' + book + 'success!!!')
} else {
console.log('The book has been borrowed!!!')
}
}
// test
// book list object
var bookList = new List()
// borrower list object
var borrowerList = new List()
// save book to list
saveBooksToList('book.txt')
console.log('------------Currently available books-------------------')
// display book information
displayList(bookList)
console.log('-----------------Start borrowing books-------------------')
// borrow book
borrowBook('xgq', 'Nodejs详解', bookList, borrowerList)
console.log('-----------------borrowing information-------------------')
// Display the list of borrowers
displayList(borrowerList)
console.log('-----------------Remaining books that can be borrowed---------------')
// List of books left after borrowing
displayList(bookList)
Please point out any mistakes, thank you.
finished~~