Trying to join a two-dimensional array in Javascript

Question

I'm trying to convert a two-dimensional array to a string in order to store it in the localStorage array. However, there is something wrong with this code I cannot identify:

for(x in array) {
    if(array[x] instanceof Array) {
        array[x] = array[x].join("`");
    }
}
var string = array.join("@");
localStorage[key] = string;

Does anyone have an idea what I'm doing wrong?

As for what's wrong, by multidimensional array I mean array[0][1] etc. When input into localStorage, all the 'string' is reduced to is @, implying on the other side of the @ there are still arrays.

what is the something that is wrong? surely, you ucan say what your input is, what you expected, and what the undesired output is? — Roland Bouman
– Roland Bouman, Commented Jan 6, 2010 at 20:58
On a sidenote, you might want to consider using JSON.stringify instead of custom seperators for your purpos. — Tomas
– Tomas, Commented Nov 2, 2010 at 12:28
@Thomas - At the time of writing, JSON.stringify was not available in all the browsers (specifically, not in the stable build of Chrome). Now, I would use that, yes. — Arda Xi
– Arda Xi, Commented Nov 2, 2010 at 22:53

Jonatas Walker · Accepted Answer · 2016-12-02 11:06:40Z

34

Nowadays this is as simple as:

[[1,2],[3,4]].map(e => e.join(':')).join(';'); // 1:2;3:4

answered Dec 2, 2016 at 11:06

Jonatas Walker

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Comments

Roland Bouman · Accepted Answer · 2010-01-06 21:01:21Z

5

what is the something that is wrong? surely, you ucan say what your input is, what you expected, and what the undesired output is?

At least, if array is indeed an array, you should not use a for..in loop. That's for objects. Just use a

for (var i=0, l=array.length; i<l; i++){
    if (array[i] instanceof Array){
        array[i] = array[i].join("`");
    }
}

answered Jan 6, 2010 at 21:01

Roland Bouman

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1 Comment

vsync Over a year ago

for..in loops are ok to use for Arrays, it's not only for objects..as long as you use 'hasOwnProperty'.

Sumner Evans · Accepted Answer · 2015-02-28 05:22:11Z

2

JSON is now standard in modern browsers. You can use it to "stringify" (convert to a JSON string) and "parse" convert from a JSON string.

You can use the JSON.stringify function to convert your 2D array to JSON and stick it in localStorage. Then you can use JSON.parse to convert it back to an array.

var my2DArray = [[1, 2, 3], [4, 5, 6]];
var stringified = JSON.stringify(my2DArray);
localStorage[key] = stringified;

var backToOriginal = JSON.parse(localStorage[key]);

edited Feb 28, 2015 at 5:22

Sumner Evans

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answered Feb 27, 2015 at 23:32

user1357172

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1 Comment

Arda Xi Over a year ago

Back in January 2010, JSON wasn't available as such in stable browsers. ;)

Mark Byers · Accepted Answer · 2010-01-06 20:59:07Z

1

Javascript doesn't have two dimensional arrays. It has only ragged arrays. Your code works for me for an appropriate input:

array = [[1,2],[3,4]];
for(x in array) {
    if(array[x] instanceof Array) {
        array[x] = array[x].join("`");
    }
}
var string = array.join("@");
alert(string);

Output:

1`2@3`4

Could you show us what input you are using and what output you get?

answered Jan 6, 2010 at 20:59

Mark Byers

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Comments

James Maroney · Accepted Answer · 2010-01-06 20:58:26Z

0

Your code seems to work fine for me, testing in Firefox.

Is it failing in a specific browser?

var array = [
["a","b"],
["c","d","e"]];
for(x in array) {
    if(array[x] instanceof Array) {
        array[x] = array[x].join("`");
    }
}
var string = array.join("@");
console.log(string);

answered Jan 6, 2010 at 20:58

James Maroney

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