TypeError: Cannot read property '1' of undefined (JavaScript)-CodePudding

I'm making some functions that loop through my 2D array and check if the value in an index is matching the parameter I passed. But I keep getting this error of "TypeError: Cannot read property '1' of undefined at findBookByTitle"

Any suggestions, I have tried everything :(

const BooksInfo = [];

function addBook(BookID, BookTitle, Author, Price, Quantity){

    let newBook = [BookID,BookTitle,Author,Price,Quantity]
    BooksInfo.push(newBook);
}

addBook(1,"Start with Why","Simon Sinek", 80.0, 13);
addBook(2, "But how do it know", "J. Clark Scott", 59.9, 22);
addBook(3, "Clean Code", "Rober Cecil Martin", 50.0, 5);
addBook(4, "Zero to One", "Peter Thiel", 45.0, 12);
addBook(5, "You don't know JS", "Kyle Simpson", 39.9, 9);

//console.log(BooksInfo);

function findBookByID(BookID){
    for(i=0; i <= BooksInfo.length; i  ){
        if(BooksInfo[i][0] == BookID){
            console.log(BooksInfo[i])
        }
    }
}

function findBookByTitle(BookTitle){
    for(i=0; i <= BooksInfo.length; i  ){
        if(BooksInfo[i][1] == BookTitle){
            console.log(BooksInfo[i])
        }
    }
}

function findBookByAuthor(Author){
    for(i=0; i <= BooksInfo.length; i  ){
        if(BooksInfo[i][2] == Author){
            console.log(BooksInfo[i])
        }
    }
}

findBookByAuthor("Kyle Simpson");
findBookByID(1);
findBookByTitle("But how do it know");

CodePudding user response：

function findBookByTitle(BookTitle){
    for(i=0; i < BooksInfo.length; i  ){
        if(BooksInfo[i][1] == BookTitle){
            console.log(BooksInfo[i])
        }
    }
}

since you're looping from index 0 to the last index, can't include the last number in the booksInfo.length. e.g: here, your booksInfo.length = 5, looping from index 0 to 5, is 6 times the iteration for i(0,1,2,3,4,5)

CodePudding user response：

Make your life so much easier (and your code so much more concise and readable) by using objects instead of representing each book in an array:

const BooksInfo = [];

function addBook(BookID, BookTitle, Author, Price, Quantity){
    let newBook = {BookID,BookTitle,Author,Price,Quantity};
    BooksInfo.push(newBook);
}

addBook(1,"Start with Why","Simon Sinek", 80.0, 13);
addBook(2, "But how do it know", "J. Clark Scott", 59.9, 22);
addBook(3, "Clean Code", "Rober Cecil Martin", 50.0, 5);
addBook(4, "Zero to One", "Peter Thiel", 45.0, 12);
addBook(5, "You don't know JS", "Kyle Simpson", 39.9, 9);

function findBookByID(BookID){
    return BooksInfo.find(book => book.BookID === BookID);
}

function findBookByTitle(BookTitle){
    return BooksInfo.find(book => book.BookTitle === BookTitle);
}

function findBookByAuthor(Author){
    return BooksInfo.find(book => book.Author === Author);
}

console.log(findBookByAuthor("Kyle Simpson"));
console.log(findBookByID(1));
console.log(findBookByTitle("But how do it know"));