Javascript Multi-Dimensional Array Problems

Question

I can't figure away around this, I want the MD array to store the name of a book and the price. I know this is easier with two arrays but really wanted to give a MD array ago in javascript. I have tried several ways but can only get the book name or the book price to display twice. Any help would be greatly appreciated.

var bookName = new Array();
for (var i = 0; i < 3; i++) 
{
bookName[i] = new Array();
 for (var j = 0; j < 1; j++) 
 {
 bookName[i] = prompt("Please enter book name!");
 bookName[[i][j]] = prompt("Please enter book price!");
 document.write(bookName[i] + bookName[[i][j]] + "</br>");
 }
}

• Peter Olson: I'm not sure what sort of structure you're wanting. Are you wanting to make it do something like [["name", "price"], ["name2", "price2"]]"?

Answer 1

I think you should just use an array of objects for this:

var books = [];
for(var i = 0; i < 3; i++) {
 books.push({
 name: prompt("Please enter book name!"),
 price: prompt("Please enter book price!")
 });
 document.write(books[i].name + books[i].price + "</br>"); 
}

If you prefer, you can do an array of arrays instead:

var books = [];
for(var i = 0; i < 3; i++) {
 books.push([prompt("Please enter book name!"), prompt("Please enter book price!")]);
 document.write(books[i][0]+ books[i][1] + "</br>"); 
}

• pseudosavant: There are many valid solutions here, but this is probably the one I would use. Most concise and easiest to follow.

Answer 2

Here is how you build a 2D array:

var bookName = new Array();
for (var i = 0; i < 3; i++) 
{
 bookName[i] = new Array();
 bookName[i][0] = prompt("Please enter book name!");
 bookName[i][1] = prompt("Please enter book price!");
 document.write(bookName[i] + bookName[i][0] + ": " + bookName[i][1] + "</br>");
}

You could also do that with objects inside the array:

var bookName = new Array();
for (var i = 0; i < 3; i++) 
{
 bookName[i] = {};
 bookName[i]["name"] = prompt("Please enter book name!");
 bookName[i]["price"] = prompt("Please enter book price!");
 document.write(bookName[i] + bookName[i].name + ": " + bookName[i].price + "</br>");
}

• Peter Olson: And use object literals and array literals instead of repeated bookName[i][prop] assignments
• bfavaretto: @Peter, I like your answer, I'd certainly code it in a similar way. But on this answer, I decided to keep the code structure closer to the OP code, because I thought it would be easier for him to understand.

Answer 3

Instead of this:

bookName[i] = prompt("Please enter book name!");
bookName[[i][j]] = prompt("Please enter book price!");
document.write(bookName[i] + bookName[[i][j]] + "</br>");

Do this:

bookName[i][j][0] = prompt("Please enter book name!");
bookName[i][j][1] = prompt("Please enter book price!");
document.write(bookName[i][j][0] + bookName[i][j][1] + "</br>");

I don't think I've ever seen var[[i][j]] format before...

Answer 4

u r overwriting your bookName[i]

bookName[i] = new Array(); and bookName[i] = prompt("Please enter book name!");

try this:

var bookName = new Array();
for (var i = 0; i < 3; i++) {
 bookName[i] = new Array();
 for (var j = 0; j < 1; j++) {
 var name = prompt("Please enter book name!");
 var price = prompt("Please enter book price!");
 bookName[i][j] = {name:name, price:price}
 document.write(bookName[i][j].name + bookName[i][j].price + "</br>");
 }
}

• J. Doe: Can you explain what this part is doing please? bookName[i][j] = {name:name, price:price}
• Churk: It is assign bookName[i][j] an hashmap like object with key = name and value = (variable name), and same with price key = 'price' and value = price (variable)

Answer 5

A multidimensional array doesn't make much sense here, you probably want an array of objects.

var books = [], i = 3;
while( i-- ) {
 books.push({
 name: prompt("Please enter book name!"),
 price: prompt("Please enter book price!")
 });
}

Answer 6

I'm not sure what you are doing there. Please make yourself familiar with the concept of Arrays, Objects and accessing of properties in JavaScript.

var bookName = new Array();

for (var i = 0; i < 3; i++) 
{
bookName[i] = new Array();
// the i. item of bookname holds an empty array now
 for (var j = 0; j < 1; j++) 
 {
 bookName[i] = prompt("Please enter book name!");
// you're overwriting the array just created with a string now
 bookName[[i][j]] = prompt("Please enter book price!");
// this is absolutely invalid syntax
 document.write(bookName[i] + bookName[[i][j]] + "</br>");
// as well as this
 }
}

What you wanted to do:

var bookName = new Array();
for (var i = 0; i < 3; i++) {
 bookName[i] = new Array();
 for (var j = 0; j < 1; j++) {
 // this is absolute ugly in a for loop:
 if (j==0)
 bookName[i][j] = prompt("Please enter book name!");
 else if (j==1)
 bookName[i][j] = prompt("Please enter book price!");
 }
 // direct accessing is better:
 document.write(bookName[i][0] + bookName[i][1] + "</br>");
}

but it would be much easier so:

var bookName = [];
for (var i = 0; i < 3; i++) {
 bookName[i] = {
 name: prompt("Please enter book name!"),
 price: prompt("Please enter book price!")
 };
 document.write(bookName[i].name + bookName[i].price + "</br>");
}

Answer 7

var bookName = [];
for (var i = 0; i < 3; i++)
{
 var b = bookName[i];
 b = [];
 for (var j = 0; j < 1; j++) 
 {
 bookName[i] = prompt("Please enter book name!");
 b[j] = prompt("Please enter book price!");
 document.write(bookName[i] + b[j] + "</br>");
 }
}

This should do it..