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London | 26-ITP-May | Damilola Odumosu | Sprint 2 | Book Library #533

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London | 26-ITP-May | Damilola Odumosu | Sprint 2 | Book Library #533

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16 changes: 7 additions & 9 deletions debugging/book-library/index.html
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Original file line number Diff line number Diff line change
@@ -1,12 +1,9 @@
<!DOCTYPE html>
<html>
<html lang="">
<head>
<title> </title>
<meta
charset="utf-8"
name="viewport"
content="width=device-width, initial-scale=1.0"
/>
<title>Book Library</title>
<meta charset="utf-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js"></script>
Expand All @@ -31,15 +28,15 @@ <h1>Library</h1>
<div class="form-group">
<label for="title">Title:</label>
<input
type="title"
type="text"
class="form-control"
id="title"
name="title"
required
/>
<label for="author">Author: </label>
<input
type="author"
type="text"
class="form-control"
id="author"
name="author"
Expand All @@ -51,6 +48,7 @@ <h1>Library</h1>
class="form-control"
id="pages"
name="pages"
min="1"
required
/>
Comment on lines 48 to 53

@cjyuan cjyuan Aug 10, 2026

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Could you find out why the browser does not check if the value in this input field is a positive whole number (even if when the constraints min="1" is specified)?

<label class="form-check-label">
Expand Down
132 changes: 65 additions & 67 deletions debugging/book-library/script.js
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Original file line number Diff line number Diff line change
@@ -1,103 +1,101 @@
let myLibrary = [];

@cjyuan cjyuan Aug 10, 2026

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Can we declare myLibrary in a way that prevents it from being accidentally reassigned?


window.addEventListener("load", function (e) {
window.addEventListener("load", function () {
populateStorage();
render();
});

function Book(title, author, pages, check) {
this.title = title;
this.author = author;
this.pages = pages;
this.check = check;
}
function populateStorage() {
if (myLibrary.length == 0) {
let book1 = new Book("Robison Crusoe", "Daniel Defoe", "252", true);
if (myLibrary.length === 0) {
let book1 = new Book("Robison Crusoe", "Daniel Defoe", 252, true);
let book2 = new Book(
"The Old Man and the Sea",
"Ernest Hemingway",
"127",
127,
true
);
myLibrary.push(book1);
myLibrary.push(book2);
render();
}
}

const title = document.getElementById("title");
const author = document.getElementById("author");
const pages = document.getElementById("pages");
const check = document.getElementById("check");
const titleInput = document.getElementById("title");
const authorInput = document.getElementById("author");
const pagesInput = document.getElementById("pages");
const checkInput = document.getElementById("check");
Comment on lines +28 to +31

@cjyuan cjyuan Aug 10, 2026

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Common practice is to declare all shared variables/constants at the beginning of the file before function definitions.


//check the right input from forms and if its ok -> add the new book (object in array)
//via Book function and start render function
function submit() {
if (
title.value == null ||
title.value == "" ||
pages.value == null ||
pages.value == ""
titleInput.value.trim() === "" ||
pagesInput.value.trim() === "" ||
authorInput.value.trim() === ""
) {
alert("Please fill all fields!");
return false;
} else {
let book = new Book(title.value, title.value, pages.value, check.checked);
library.push(book);
let book = new Book(
titleInput.value,
authorInput.value,
Number(pagesInput.value),
checkInput.checked
);
Comment on lines +42 to +47

@cjyuan cjyuan Aug 10, 2026

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  • Is Number(pagesInput.value) always a valid positive whole number?

  • The code checks the trimmed value but it uses the raw values.

    A better and safer approach to deal with user input is to first store the preprocessed input in variables, validate them, then use those cleaned values consistently throughout the rest of the code.

myLibrary.push(book);
render();
}
}

function Book(title, author, pages, check) {
this.title = title;
this.author = author;
this.pages = pages;
this.check = check;
}

function render() {
let table = document.getElementById("display");
let rowsNumber = table.rows.length;
//delete old table
for (let n = rowsNumber - 1; n > 0; n-- {
table.deleteRow(n);
}
tableBody.innerHTML = "";
//insert updated row and cells
let length = myLibrary.length;
for (let i = 0; i < length; i++) {
let row = table.insertRow(1);
let titleCell = row.insertCell(0);
let authorCell = row.insertCell(1);
let pagesCell = row.insertCell(2);
let wasReadCell = row.insertCell(3);
let deleteCell = row.insertCell(4);
titleCell.innerHTML = myLibrary[i].title;
authorCell.innerHTML = myLibrary[i].author;
pagesCell.innerHTML = myLibrary[i].pages;
myLibrary.forEach((book, i) => {
createBookRow(book, i);
});
}

const tableBody = document.querySelector("tbody");

@cjyuan cjyuan Aug 10, 2026

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Why not keep this variable declaration with the other variable declarations at the beginning of the file?

let readStatus;

@cjyuan cjyuan Aug 10, 2026

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Does readStatus need to be shared among functions? If not, it is better to declare it as a local variable in the function where it is used.


//add and wait for action for read/unread button
let changeBut = document.createElement("button");
changeBut.id = i;
changeBut.className = "btn btn-success";
wasReadCell.appendChild(changeBut);
let readStatus = "";
if (myLibrary[i].check == false) {
readStatus = "Yes";
} else {
readStatus = "No";
}
changeBut.innerText = readStatus;
function createBookRow(book, index) {
const changeBtn = document.createElement("button");
const deleteBtn = document.createElement("button");

changeBut.addEventListener("click", function () {
myLibrary[i].check = !myLibrary[i].check;
render();
});
let row = tableBody.insertRow(-1);
let titleCell = row.insertCell(0);
let authorCell = row.insertCell(1);
let pagesCell = row.insertCell(2);
let wasReadCell = row.insertCell(3);
let deleteCell = row.insertCell(4);

//add delete button to every row and render again
let delButton = document.createElement("button");
delBut.id = i + 5;
deleteCell.appendChild(delBut);
delBut.className = "btn btn-warning";
delBut.innerHTML = "Delete";
delBut.addEventListener("clicks", function () {
alert(`You've deleted title: ${myLibrary[i].title}`);
myLibrary.splice(i, 1);
render();
});
titleCell.textContent = book.title;
authorCell.textContent = book.author;
pagesCell.textContent = book.pages;
wasReadCell.appendChild(changeBtn);
deleteCell.appendChild(deleteBtn);
deleteBtn.textContent = "Delete";
changeBtn.className = "btn btn-success";

deleteBtn.className = "btn btn-warning";

if (!book.check) {
readStatus = "No";
} else {
readStatus = "Yes";
}
changeBtn.innerText = readStatus;
Comment on lines +86 to +91

@cjyuan cjyuan Aug 10, 2026

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This could be a good opportunity to practice using the ? : conditional operator. Could you rewrite the code on lines 86–91 as a single statement?

changeBtn.addEventListener("click", function () {
book.check = !book.check;
render();
});
deleteBtn.addEventListener("click", function () {
alert(`You've deleted title: ${book.title}`);
myLibrary.splice(index, 1);
render();
Comment on lines +97 to +99

@cjyuan cjyuan Aug 10, 2026

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The alert message is shown before the book is actually deleted; the deletion only occurs after the alert dialog is dismissed. This introduces a risk that the operation may not complete (e.g., if the user closes the browser before dismissing the alert).

In general, it’s better to display a confirmation message only after the associated operation has successfully completed.

In addition, alert() is a blocking function call. As a result, invoking it prevents the browser from updating the UI until the dialog is dismissed.

Suggestion: Research for approaches that allows the UI to update before displaying the alert dialog.

});
}
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