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.

Answer 1

现在这很简单：

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

Answer 2

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("`");
    }
}

Answer 3

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]);

Answer 4

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?

Answer 5

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);