How to get all values out of array and its sub-arrays

Question

I'm trying to build a function that will be applied to an array and will extract all its values which are not arrays.

For the ones that are arrays, it will do the same process again until all the values from the first array, its sub-arrays, the sub-arrays' own sub-arrays and so on will be put into a single array.

The problem I'm facing lies upon the fact that I won't know beforehand how many sub-arrays each array will have and so on.

What I've tried:

I have tried using forEach() as shown below, but as I said above the number of sub-arrays and the values in general is unknown beforehand. I'm sure that some kind of looping or maybe even recursion would help, but I can't get it to work in my mind.

function extract (value) {    
    var
        result = [],
        isArray = function (value) {
            return value.constructor === Array;
        }

    if (isArray(value)) {
        value.forEach(function (each) {
            if (!isArray(each)) result.push(each);
            else {
                each.forEach(function (j) {
                    if (!isArray(each)) result.push(each);
                    else... // same as above
                });
            }
        });
    }

    return result;
}

I believe that using each = each[i] as if I were looking for descendant in the DOM would help, but I'm not sure how to set up the while loop in this case and what the terminating condition should be.

Desired Result:

var array = [["a", 2, [3, "mn"], "bu"], "la", [12, 34, "ab"]]; // Just an example
var result = extract(array); // Outputs: ["a", 2, 3, "mn", "bu", "la", 12, 34, "ab"]

How can I fix my current code in order to achieve the desired result above?

I think this answer will solve your problem: http://stackoverflow.com/a/15030117/693275 — Rob M., Aug 31 '16 at 22:54
It's using `reduce()` which is for IE9+. Thanks though @RobM. — Angel Politis, Aug 31 '16 at 22:59
Check some of the other examples (there are many) - it's really the same question — Rob M., Aug 31 '16 at 23:00

score 1 · Accepted Answer · 2016-08-31T23:01:30.073

1

A solution with recursion:

function extract( array, newarray ){
    if( !newarray ) newarray = [] ;
    if( array ) for( var i = 0 ; i < array.length ; ++i )
    {
        if( array[i].constructor.name === "Array" ) extract( array[i], newarray ) ;
        else newarray.push( array[i] ) ;
    }
    return newarray ;
}
var array = [["a", 2, [3, "mn"], "bu"], "la", [12, 34, "ab"]]; // Just an   
var newarray = extract(array); // Outputs: ["a", 2, 3, "mn", "bu", "la", 12, 34, "ab"]
console.log( newarray ) ;

edited Aug 31 '16 at 23:01

answered Aug 31 '16 at 22:52

Excellent! Thanks @sjdalessandro. – Angel Politis Aug 31 '16 at 23:02
@AngelPolitis You are welcome. Glad to help! – Aug 31 '16 at 23:04

score 1 · Answer 2 · answered Sep 01 '16 at 00:36

1

You could do this very simply with a recursive reduce function.

function flatten(arr) {
  return arr.reduce(function(a, b) {
    return a.concat(Array.isArray(b) ? flatten(b) : b);
  }, []);
}

var arr = [["a", 2, [3, "mn"], "bu"], "la", [12, 34, "ab"]];
var result = flatten(arr);
console.log(result);

answered Sep 01 '16 at 00:36

KevBot

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You're **`reduce()`** which is for IE9+. Thanks for your answer though. – Angel Politis Sep 01 '16 at 00:37
Ah, I didn't see the comment above before going for this. :/ – KevBot Sep 01 '16 at 00:38
Well, since it's working, it may be helpful for somebody in the future. Upvoted :) – Angel Politis Sep 01 '16 at 00:39

How to get all values out of array and its sub-arrays

2 Answers2