horizontal to vertical in a javascript array

Question

I have the sample code below;

var myarray= [],
myarray2=[];
var L=100;
for(j =0; j< 4;j++){
    for(i =0; i<4;i++){        
       myarray.push([L]);
       L=L+100;
    }
    myarray2.push(myarray);
    alert(myarray2[j]);
}

The output will be

100,200,300,400,500,600,700,800,900,100,1100,1200,1300,1400,1500,1600

Is it possible to sort the values like below in an array within an array?

100, 500, 900, 1300
200, 600, 1000, 1400
300, 700, 1100, 1500
400, 800, 1200, 1600

I would appreciate any help....thanks in advance.

Is myarray2 really supposed to contain 4 references to the same myarray? — Bergi
– Bergi, Commented May 2, 2013 at 21:47
Are you wanting to create the array in that format or alter the flat array to that format? — Xotic750
– Xotic750, Commented May 2, 2013 at 21:47
Why don't you create that 2d-array you want as result in the first place? — Bergi
– Bergi, Commented May 2, 2013 at 21:48
I need just a little more information. Are you looking to achieve is in an alert message of would you be open to an HTML approach. Also are you trying to arrang these in colums that are no longer than 4 or in no more than 4 columns no matter the length? — Jason Sperske
– Jason Sperske, Commented May 2, 2013 at 21:49

Xotic750 · Accepted Answer · 2013-05-02 22:51:31Z

2

This solution will convert from your flat array into the multidimentional array that you have described.

Javascript

var array = "100,200,300,400,500,600,700,800,900,100,1100,1200,1300,1400,1500,1600".split(",");
var grouping = 4;
var result = [];

array.forEach(function (element, index) {
    var group = index % grouping;
    var temp = result[group];

    if (!Array.isArray(temp)) {
        temp = [];
    }

    temp.push(element);
    result[group] = temp;
});

console.log(result);

On jsfiddle

UPDATE:

Ok, I am going to assume that it is myarray, as suggested by @bergi, that you wish to convert and not myarray2. Based on this assumption here is a modified solution

Javascript

var myarray = [],
    myarray2 = [];
var L = 100;
for (var j = 0; j < 4; j++) {
    for (var i = 0; i < 4; i++) {
        myarray.push([L]);
        L = L + 100;
    }

    myarray2.push(myarray);
}

var columns = 4;
var result = [];
var flattened = myarray.toString().split(",");
var length = flattened.length;
var rows = Math.round(length / columns);

flattened.forEach(function (element, index) {
    var group = index % rows;
    var temp = result[group];

    if (!Array.isArray(temp)) {
        temp = [];
    }

    temp.push(element);
    result[group] = temp;
});

console.log(result);

On jsfiddle

Here is an alternative flatten method

var flattened = myarray.reduce(function(a, b) {
    return a.concat(b);
});

if you don't like

var flattened = myarray.toString().split(",");

And for interest only sake, the jsperf on the above flatten methods.

edited May 2, 2013 at 22:51

answered May 2, 2013 at 21:56

Xotic750

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2 Comments

Bergi Over a year ago

Actually, his myArray is [[100],[200],[300],[400],[500],[600],[700],[800],[900],[1000],[1100],[1200],[1300],[1400],[1500],[1600]] - that array string is only the output if you alert it.

Xotic750 Over a year ago

Aha, thanks, I didn't look at what he actually created, just what he stated.

mzedeler · Accepted Answer · 2013-05-02 22:00:44Z

0

This will generate an array of arrays from scratch.

var x = 10;
var y = 4; 
var result = [];

for(j = 0; j < y; j++) {
  result[j] = [];
  for(i = 0; i < x; i++) {
    result[j].push((j % y + i*y) * 100);
  }
}

console.log(result);

Yields:

[ [   0, 400,  800, 1200, 1600, 2000, 2400, 2800, 3200, 3600 ],
  [ 100, 500,  900, 1300, 1700, 2100, 2500, 2900, 3300, 3700 ],
  [ 200, 600, 1000, 1400, 1800, 2200, 2600, 3000, 3400, 3800 ],
  [ 300, 700, 1100, 1500, 1900, 2300, 2700, 3100, 3500, 3900 ] ]

You can adjust the number of entries by changing x and y.

answered May 2, 2013 at 22:00

mzedeler

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4b0 · Accepted Answer · 2020-01-23 04:49:45Z

0

You can do this by a one liner using lodash or underscore JavaScript,

let arr=[100,200,300,400,500,600,700,800,900,100,1100,1200,1300,1400,1500,1600];
let len=4;  // Can be varied upon your requirement
let soln= _.unzip( _.chunk(arr,len)).map((x)=>{return (x!==undefined)?x:[];});
console.log(soln); // This will print resultant array

This will print the following result.

[ [ 100, 500, 900, 1300 ],

[ 200, 600, 100, 1400 ],

[ 300, 700, 1100, 1500 ],

[ 400, 800, 1200, 1600 ] ]

edited Jan 23, 2020 at 4:49

4b0

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answered Jan 23, 2020 at 4:46

Rocking Rohit

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