Mix (or sort) JS array

Question

I have the only array:

[0, 1, 2, 3, 4, 5, 6, 7, 8]

The "first half" of array's data is [0,1,2,3,4] and the second is [5,6,7,8].

Now I should get something like this (it is not random mixing)

[0, 5, 1, 6, 2, 7, 3, 8, 4]

This is an array of data for two columns. I should place first half of data in first column, and the second one in second column.

I'm trying to find a simple solution... Thanks for advice!

See https://stackoverflow.com/questions/2450954/how-to-randomize-shuffle-a-javascript-array. — Kirill Bulygin, May 30 '17 at 11:09
@NinaScholz Sorry for my English) In my first example the array.length = 9, and the "half" is Math.ceil(array.length/2) => 5 ... — Andrew Koshkin, May 30 '17 at 11:13

Nenad Vracar · Accepted Answer · 2017-05-30T11:26:00.033

3

You can split your array in half using Math.ceil to round up number and then loop first part and add each element from second part incrementing counter by 2.

var arr = [0, 1, 2, 3, 4, 5, 6, 7, 8], c = 1

var half = arr.splice(Math.ceil(arr.length / 2))
half.forEach(e => (arr.splice(c, 0, e), c += 2))

console.log(arr)

edited May 30 '17 at 11:26

answered May 30 '17 at 11:20

Nenad Vracar

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Perfect solution. – Andrew Koshkin May 30 '17 at 11:35

Aloïs de La Comble · Answer 2 · 2017-05-30T11:36:47.760

1

Try the following, using map and an inline if statement

    var array = [0,1,2,3,4,5,6,7,8]
    var result = array.map(function(item,index){
      return (index%2 == 0) ? array[index/2] :  array[Math.floor((index+array.length)/2)];
    });
    console.log(result);

edited May 30 '17 at 11:36

answered May 30 '17 at 11:20

Aloïs de La Comble

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You probably want `index>>1` not `index/2` here. Your note is valid for python2, for example, but JS will give you a float. – georg May 30 '17 at 11:23
I added a code snippet, index/2 gives floor(index/2), it is a number not a float – Aloïs de La Comble May 30 '17 at 11:27
1

@AloïsdeLaComble And now Increase an array length by 1... result went wrong – Andrew Koshkin May 30 '17 at 11:29
1

You are right ! My mistake ! It works with Math.floor – Aloïs de La Comble May 30 '17 at 11:37

Nina Scholz · Answer 3 · 2017-05-30T12:18:49.367

You could calculate the index and map the value from the array.

(i >> 1) + ((i & 1) * ((a.length + 1) >> 1))
^^^^^^^^                                     take the half integer value
            ^^^^^^                           check for odd
                          ^^^^^^^^^^^^       adjust length
                       ^^^^^^^^^^^^^^^^^^^^  the half value of adjusted length

var array = [0, 1, 2, 3, 4, 5, 6, 7, 8],
    result = array.map((_, i, a) => a[(i >> 1) + ((i & 1) * ((a.length + 1) >> 1))]);

console.log(result);

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Mix (or sort) JS array

3 Answers3