Generating an array with sub-arrays

Question

I realize this is a somewhat off manner of operations, but for the sake of possibility, I'm wondering if anyone can help?

Here array2 is holding the end state I would like array1 to hold (only I want to do it with the for loop. It's fine that each sub_array's have to be initialized as their own variables, I'm just trying to get the array1 to hold N number of sub_arrays via the loop.

Here is the example I've tried, but trying to "compile" it via a string doesn't allow the sub_arrays to be called in a useable manner.

var numberOfSubArrays = 3
var sub_array1 = []
var sub_array2 = []
var sub_array3 = []

var array1 = []
var array2 = [sub_array1,sub_array2,sub_array3]

for (var i = 0; i < numberOfSubArrays; i++) {
    array1[i] = "sub_array" + i
}

Any thoughts would be much appreciated!

Do you mean array1[i] = array2[i]? Or perhaps some kind of concat? — mplungjan
– mplungjan, Commented Feb 7, 2016 at 6:55
Or for (var i = 0; i < numberOfSubArrays; i++) { eval("array1[" + i +"] = sub_array" + i); } — Rajaprabhu Aravindasamy
– Rajaprabhu Aravindasamy, Commented Feb 7, 2016 at 6:55
@mplungjan array2 is an array holding references of other arrays. If it was an object with keys sub_array1....n then we could do just like you advised. Am i right? — Rajaprabhu Aravindasamy
– Rajaprabhu Aravindasamy, Commented Feb 7, 2016 at 7:03

Gavriel · Accepted Answer · 2016-02-07 07:07:19Z

1

var numberOfSubArrays = 3
var sub_array1 = [1]
var sub_array2 = [2]
var sub_array3 = [3]

var array1 = []
// we don't need array2 at all
//var array2 = [sub_array1,sub_array2,sub_array3]

// you need to count from 1..n, as you named your sub_arrays like that
for (var i = 1; i <= numberOfSubArrays; i++) {
    // you can use eval, but be careful, eval is evil!
    array1[i-1] = eval("sub_array" + i)
}
console.log(array1);

edited Feb 7, 2016 at 7:07

answered Feb 7, 2016 at 6:56

Gavriel

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4 Comments

Fuego DeBassi Over a year ago

Yes! I just didn't know eval was a thing. Many thanks

Gavriel Over a year ago

Right, but I think the intention was not to have the array2 in the code :)

J. V. A. Over a year ago

I think array2 was just to show us what they want in array1 -- as in references to the arrays, not just their names as strings.

J. V. A. Over a year ago

BTW, see my answer for an eval-free and BPA-free alternative :)

J. V. A. · Accepted Answer · 2016-02-07 07:08:50Z

1

Using eval is yucky. This will work in browsers:

var numberOfSubArrays = 3
var sub_array1 = []
var sub_array2 = []
var sub_array3 = []

var array1 = []
var array2 = [sub_array1,sub_array2,sub_array3]

for (var i = 0; i < numberOfSubArrays; i++) {
    array1[i] = window["sub_array" + i + 1];
}

In browsers, "global" vars are really objects in "window". Note: this will not work in tools like jsfiddle, because they put your code inside a function (that you don't see).

answered Feb 7, 2016 at 7:08

J. V. A.

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