Create a JS multidimensional array from string

Question

I would like to create a miltidimentional array as follows so

var multi-arr = [
                  ["A,2,5"], 
                  ["B,4,4"], 
                  ["C,4,4"]
                ]

from string values gotten from the database using ajax.

string data gotten from db delimited by #

var string = "A,2,5# B,4,4# C,4,4";

I split the string by a '#' delimiter

arr1=string.split(/\s*\#\s*/g);

creating the array below

var arr = ["A,2,5", "B,4,4", "C,4,4"];

I want to further split the items in the above array using the comma ',' as a delimiter and create a multidimensional array

My problem is the loop only pushes in the last item in the array

for (i = 0; i < arr.length; i++) {  
        var arr2 = [];
        arr2[i]=arr2.push(arr1[i].split(/\s*\,\s*/g));
    }

console.log(arr2);

What am i doing wrong? or what can i do better?

why not rewrite it to JSON and just parse that?

Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans

2016-01-24 01:33:36 +00:00
Commented Jan 24, 2016 at 1:33 — Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans, Commented Jan 24, 2016 at 1:33

Mike 'Pomax' Kamermans · Accepted Answer · 2016-01-24 01:46:51Z

4

You could split it, but you have all the delimiters in place anyway, just rewrite your string to be JSON-conformant and run it through JSON.parse():

// base string
var str = "A,2,5# B,4,4# C,4,4";

// quote text data. If the array was plain number data, we don't even need this step.
var quoted = str.replace(/([a-zA-Z]+)/g,'"$1"');

// rewrite to JSON form for a nested array
var jsonStr = "[[" + quoted.replace(/#/g,'],[') + "]]";

// done, just tell the JSON parser to do what it needs to do.
var arr = JSON.parse(jsonStr);

And that's it, arr is now the nested array [["A",2,5],["B",4,4],["C",4,4]].

edited Jan 24, 2016 at 1:46

answered Jan 24, 2016 at 1:37

Mike 'Pomax' Kamermans

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Comments

mani · Accepted Answer · 2016-01-24 01:39:51Z

2

This should work

var str = "A,2,5# B,4,4# C,4,4";
var arr = str.split(/\s*\#\s*/g);
    for (var i = 0; i < arr.length; i++) {  
        arr[i]=arr[i].split(/\s*\,\s*/g);
    }
console.log(arr)

In your solution var arr2 = []; needs to be outside the for loop, or it gets redefined everytime. However, we don't really need to define a separate var and simply update the original array.

edited Jan 24, 2016 at 1:39

answered Jan 24, 2016 at 1:31

mani

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Comments

user2182349 · Accepted Answer · 2016-01-24 01:33:03Z

1

The var statement should be outside the for loop and you don't need to do the assignment and the push.

var i;
var string = "A,2,5# B,4,4# C,4,4";
var arr1 = string.split("#");
var arr2 = [];
for (i = 0; i < arr1.length; i++) {
        arr2[i]=arr1[i].split(",");
}   

console.log(arr2);

As suggested by Mike 'Pomax' - you could return the data from the server as JSON. If you're using PHP, that can be done like so:

header('Content-Type: application/json');
echo json_encode($queryResult);
exit;

answered Jan 24, 2016 at 1:33

user2182349

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3 Comments

Victor Njoroge Over a year ago

That's what i was doing wrong. But i'll use Mike 'Pomax' s method.

Mike 'Pomax' Kamermans Over a year ago

just remember not to trust your server's response (becaue 404s, 500s, etc), and use a try/catch, because if you're feeding data to JSON.parse() without knowing for certain what's in it (like in my answer), it can throw and cause your script to error out.

user2182349 Over a year ago

For fun - you can compare the performance of these solutions: jsperf.com/string-to-multi-array. Performance will likely vary on different data sets, one one of these solutions has an additional check on the content of the array.

gfpacheco · Accepted Answer · 2016-01-24 01:44:08Z

1

Here is a simple solution that should work on modern browsers:

var string = "A,2,5# B,4,4# C,4,4";
var multiArray = string.split(/\s*\#\s*/g).map(function(substr) {
  return [substr];
});

edited Jan 24, 2016 at 1:44

answered Jan 24, 2016 at 1:38

gfpacheco

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Comments

synthet1c · Accepted Answer · 2016-01-24 01:39:29Z

You just need to loop over each element in the array again after your first split. I would use Array.prototype.map as it will return you a new array without mutating the original.

I also did a check to see if the value in the inner array was a number. if it was it is parsed to an actual number.

var arr = ["A,2,5", "B,4,4", "C,4,4"];

console.log(arr);

var multidimensional = arr.map(function(item) {
  // you need to split the elements in your array
  return item.split(/,/).map(function(val) {
    // you may as well check if it's a string or a Number
    return parseIfNumber(val);
  })
});

console.log(multidimensional);

// helper functioon
function parseIfNumber(val) {
  return /^[0-9.-]+$/.test(val) 
    ? Number(val) 
    : val;
}

<script src="http://codepen.io/synthet1c/pen/WrQapG.js"></script>

jeffdill2 · Accepted Answer · 2016-01-24 01:44:10Z

0

From your current arr variable - ["A,2,5", "B,4,4", "C,4,4"] - you can create your multi_arr variable like so:

var multi_arr = [];

arr.forEach(function(a) {
  multi_arr.push([a]);
});

Keep in mind, this will create the array exactly as the example of what you were looking for, which was this:

var multi-arr = [
                  ["A,2,5"], 
                  ["B,4,4"], 
                  ["C,4,4"]
                ]

If you want each of the items in the inner arrays to be split as well, this will work for you:

var multi_arr = [];

arr.forEach(function(a) {
  multi_arr.push(a.split(','));
});

edited Jan 24, 2016 at 1:44

answered Jan 24, 2016 at 1:35

jeffdill2

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