Multidimensional array in Javascript: Cannot set property '0' of undefined

Question

I'm trying to build an array of strings, but I got an

Uncaught TypeError: Cannot set property '0' of undefined

I don't really get why, here is my code.

$("#tableLits > tbody > tr input").filter(function(){ return $(this).val() !== '' }).each(function(){
    nom = $(this).attr('name');
    numChambre = parseInt(nom.charAt(nom.length-1));
    taille = nom.slice(nom.charAt(nom.length-2),-2).replace('lit','');          
    chambres[numChambre][nbLits] = taille;              
    nbLits = oldChambre == numChambre ? nbLits++ : 0;
    oldChambre = numChambre;
});
console.log(chambres);

The error is on this line:

chambres[numChambre][nbLits] = taille;

But when I look at the debugger,

Chambre is an array
numChambre = 1
nbLit = 0

My goal is to assign a size of a bed (taille) to a bed number (nbLit) in a given room (chambres)

Edit

For example, I have this: lit80n1 lit90n1 lit120n2 lit160n3

And I want to output something like this:

Chambre 1 -> 1 bed : 80cm, 1 bed : 90cm
Chambre 2 -> 1 bed : 120 cm
Chambre 3 -> 1 bed : 160cm

Felix Kling · Accepted Answer · 2013-04-30 12:35:46Z

4

JavaScript does not have multi-dimensional arrays. What you can have is an array of arrays, but you have to initialise each "sub-array" explicitly:

if (!chambres[numChambre]) {
    chambres[numChambre] = [];
}
chambres[numChambre][nbLits] = taille;

answered Apr 30, 2013 at 12:35

Felix Kling

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5 Comments

Felix Kling Over a year ago

@VisioN: If you want to be explicit, yes (though personally I'd prefer typeof). But I think in a controlled environment, this would be sufficient.

VisioN Over a year ago

Agree, and let's hope that chambres[numChambre] will never become falsy.

Kai23 Over a year ago

Thansk for the answer. It almost works, the « problem » is that it overwrite my first « nbLit ». So, instead of 4 elements, I have 3 arrays with only one element in the inside.

Felix Kling Over a year ago

@Kai23: The values for numChambre and nbLits might not be what you expect or this might not be the right approach to create the data structure you want, I don't know. Read this to learn how to debug JavaScript and inspect your code and variables.

Kai23 Over a year ago

Just had to do this : nbLits = (oldChambre == numChambre) ? nbLits + 1 : 0;

VisioN · Accepted Answer · 2013-04-30 12:35:56Z

1

Before adding elements to the second dimension of the array you need to define it:

chambres[numChambre] = [];
chambres[numChambre][nbLits] = taille;

answered Apr 30, 2013 at 12:35

VisioN

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