Iterate over a multidimensional javascript array and create new array?

Question

I have a multidimensional JavaScript array with some string data.

var array = [];

array[0] = ["A","B","C"];  
array[1] = ["G","H"];

I want to merge these together into a new array.

Value 1 from the first array should merge with value 1 from array 2 and so on.

Of course, I can do like this.

var array2 = array[0][0] + array[1][0];

But I don't the data so the first array could hold 6 values and there could also be more than 2 arrays.

Is there a way to dynamically iterate over the multidimensional array and create a new array.

please add the expected output and the code that you had tried — Pranav C Balan
– Pranav C Balan, Commented Aug 12, 2016 at 12:47

Pranav C Balan · Accepted Answer · 2016-08-12 13:09:56Z

1

You can use Array#map and Array#join methods.

// iterate over multi diamensional array and
// generate array with first element of each nested array
var array2 = array.map(function(v){ 
   // retrieve the first element
   return v[0]; 
   // join them to convert into a string as your output
}).join('')

var array = [];

array[0] = ["A", "B", "C"];
array[1] = ["G", "H"];

var array2 = array.map(function(v) {
  return v[0];
}).join('')

console.log(array2);

If you want to do the same with all index then use Array#reduce method.

var array = [];

array[0] = ["A", "B", "C"];
array[1] = ["G", "H"];

// iterate and reduce a single array
var array2 = array.reduce(function(arr, e) {
  // iterate over nested array 
  e.forEach(function(v, i) {
    // concatenate with the elements in parent array
    arr[i] = (arr[i] || '') + v;
  });
  return arr
  // set initial value as array
}, [])

console.log(array2);

edited Aug 12, 2016 at 13:09

answered Aug 12, 2016 at 12:59

Pranav C Balan

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2 Comments

Alex Claesson Over a year ago

Perfect. This is exactly what i need. You made my day.

Pranav C Balan Over a year ago

@AlexClaesson : glad to help :)

Beto Frega · Accepted Answer · 2016-08-12 13:04:29Z

0

I believe you need to do something like this:

myArray = [["s","m","a"],["d","f"],["t","h","r"]];

function generateStrings(array2d){
    newArray = [];

    function interate(n){
     newString = myArray.reduce((p,c)=>{return c[n]?p+c[n]:p},"")  
     console.log(newString)
     if (newString)newArray.push(newString),interate(n+1)
    }
    interate(0)

    return newArray;
}


generateStrings(myArray);

answered Aug 12, 2016 at 13:04

Beto Frega

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Comments

score 0 · Accepted Answer · 2016-08-12 13:26:05Z

0

The most compact way of writing this would be the following:

arrays[0].map((_, i) => arrays.map(array => array[i]).join(''))

Breaking it down:

arrays[0]                     // Starting with the first sub-array,
  .map(                       // create a corresponding array 
    (_, i) =>                 // whose value, for each index is,
      arrays                  // for each of the sub-arrays,
        .map(                 // an array whose values are
          array => array[i])  // the subarray at that index
        )
        .join('')             // with its elements joined together
  );

edited Aug 12, 2016 at 13:26

answered Aug 12, 2016 at 12:48

user663031

3 Comments

maowtm Over a year ago

Uncaught SyntaxError: Unexpected token [ Oops.. You need map((elt

Barmar Over a year ago

Will this work correctly if arrays[0] is shorter than the other arrays?

user663031 Over a year ago

No, but I don't know what the desired behavior is in that case.

David Gomez · Accepted Answer · 2016-08-12 13:40:06Z

0

You can use a simple reduce function to merge the Array.

const arr = [ [1, 2, 3], [4, 5] ];
const newArr = arr.reduce((acc, x) => [...acc, ...x], [])

console.log(newArr) // [1, 2, 3, 4, 5]

If you need to create an String object after the merge you just have to apply join('') on the returned array.

With Concat

This is the concat version of the function in case you want to use it.

const newArr = arr.reduce((acc, x) => acc.concat(...x), [])

edited Aug 12, 2016 at 13:40

answered Aug 12, 2016 at 13:17

David Gomez

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2 Comments

user663031 Over a year ago

This is a very clumsy way to do [].concat(...arr), which is not what the OP wants to do anyway.

David Gomez Over a year ago

Sure you can use concat too, but it wont look as good. Your choice.

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