Convert a 2D JavaScript array to a 1D array [duplicate]

Question

I want to convert a 2D JavaScript array to a 1D array, so that each element of the 2D array will be concatenated into a single 1D array.

Here, I'm trying to convert arrToConvert to a 1D array.

var arrToConvert = [[0,0,1],[2,3,3],[4,4,5]];

console.log(get1DArray(arrToConvert)); //print the converted array

function get1DArray(2dArr){
    //concatenate each element of the input into a 1D array, and return the output
    //what would be the best way to implement this function?
}

Array.join()? developer.mozilla.org/en-US/docs/JavaScript/Reference/… — Michael Berkowski
– Michael Berkowski, Commented Feb 12, 2013 at 2:00
@MichaelBerkowski It looks like Array.join() returns a string instead of an array. — Anderson Green
– Anderson Green, Commented Feb 12, 2013 at 2:02
What is your expected output? Do you mean that you want the 3 sub-arrays flattened into one array? I misunderstood I think. — Michael Berkowski
– Michael Berkowski, Commented Feb 12, 2013 at 2:03
How would you do this if some elements are arrays and some aren't. For example how would you convert ['a', 'b', 'c', 'd', ['a', 'b', 'c']] to ['a', 'b', 'c', 'd', 'a', 'b', 'c'] — Joel
– Joel, Commented Dec 4, 2023 at 15:26

Blaž Zupančič · Accepted Answer · 2019-07-13 16:12:18Z

172

Use the ES6 Spread Operator

arr1d = [].concat(...arr2d);

Note that this method is only works if arr2d has less than about 100 000 subarrays. If your array gets larger than that you will get a RangeError: too many function arguments.

For > ~100 000 rows

arr = [];
for (row of table) for (e of row) arr.push(e);

concat() is too slow in this case anyway.

The Underscore.js way

This will recursively flatten arrays of any depth (should also work for large arrays):

arr1d = _.flatten(arr2d);

If you only want to flatten it a single level, pass true as the 2nd argument.

A short < ES6 way

arr1d = [].concat.apply([], arr2d);

edited Jul 13, 2019 at 16:12

answered Oct 1, 2016 at 10:58

Blaž Zupančič

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3 Comments

AlThePal78 Over a year ago

the underscore way gives me an error when I try to use it on something simple, says that it is undefince

Blaž Zupančič Over a year ago

@daddycardona underscore.js is an external library. It will be undefined till you import it. underscorejs.org

Lucas Simões Over a year ago

Just Complementing... ES2019 introduced the .flat() method in Array Prototype. You can pass "depth" paramter in flat() method to specify how deep a nested array structure should be flattened. Defaults to 1.

Marty · Accepted Answer · 2013-02-12 02:00:36Z

46

Try .concat():

var arrToConvert = [[0,0,1],[2,3,3],[4,4,5]];
var newArr = [];


for(var i = 0; i < arrToConvert.length; i++)
{
    newArr = newArr.concat(arrToConvert[i]);
}

console.log(newArr);

answered Feb 12, 2013 at 2:00

Marty

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Comments

Anand G · Accepted Answer · 2022-06-30 16:02:40Z

34

Try .reduce()

var test2d = [
  ["foo", "bar"],
  ["baz", "biz"]
];
var merged = test2d.reduce(function(prev, next) {
  return prev.concat(next);
});

console.log(merged)

Source: http://jsperf.com/2-dimensional-array-merge

edited Jun 30, 2022 at 16:02

Anand G

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answered Oct 12, 2014 at 2:31

blvz

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Comments

marteljn · Accepted Answer · 2013-02-12 02:06:05Z

14

How about:

var arrToConvert = [[0,0,1],[2,3,3],[4,4,5]];

function get1DArray(arr){
    return arr.join().split(",");
}

console.log(get1DArray(arrToConvert));

http://jsfiddle.net/JRR4J/

answered Feb 12, 2013 at 2:06

marteljn

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2 Comments

Marty Over a year ago

What happens if the nested elements are objects rather than numbers or strings?

marteljn Over a year ago

@MartyWallace ["0", "0", "1", "2", "3", "3", "4", "4", "5", "[object Object]"] This is what happens. I see your point my solution will only work with strings and numbers.

Alan Wells · Accepted Answer · 2020-05-28 21:52:11Z

1

var arrToConvert = [[0,0,1],[2,3,3],[4,4,5]];

var modifiedArray = arrToConvert.map(function(array){ 
    return array[0]+array[1]+array[2];
});

Another Example

var passengers = [ 
  ["Thomas", "Meeks"],
  ["Gregg", "Pollack"],
  ["Christine", "Wong"],
  ["Dan", "McGaw"]
];

var modifiedNames = passengers.map(function(convArray){
    return convArray[0]+" "+convArray[1];
});

edited May 28, 2020 at 21:52

Alan Wells

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answered Feb 6, 2014 at 8:32

Balasubramanian

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Comments

Saturnix · Accepted Answer · 2013-02-12 02:19:09Z

0

var arrToConvert = [[0, 0, 1], [2, 3, 3], [4, 4, 5]];

function get1DArray(arr){

    var result = new Array();

    for (var x = 0; x < arr.length; x++){
        for (var y = 0; y < arr[x].length; y++){

        result.push(arr[x][y])

        }
    }

    return result
}


alert (get1DArray(arrToConvert))

http://jsfiddle.net/Saturnix/ReeqQ/

answered Feb 12, 2013 at 2:19

Saturnix

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Convert a 2D JavaScript array to a 1D array [duplicate]

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Use the ES6 Spread Operator

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Use the ES6 Spread Operator

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