Reducing array of items into a single array list

Question

Below is my array if items that I want to reduce it to a single list of arrays..

var input=[
    [
        2
    ],
    [
        3,
        13
    ],
    [
        4,
        14
    ],
    [
        5,
        15,
        25,
        35
    ]
]

var output=[
    2,
    3,
    13,
    4,
    14,
    5,
    15,
    25,
    35
]

My code:

  function reduceArray(item){
                  for(var i=0;i<item.length;i++){
                      return i;
                  }
              }
    var result=result.map((item)=>{
                   if(item.length>0){
                       return reduceArray(item);
                   }else{
                       return item;
                   }
               })

which produces the same result.Can anyone please figure out where I'm doing wrong or any other approach to achieve this..Thanks

Amadan · Accepted Answer · 2016-05-23T07:41:20.550

input.reduce(function(a, x) { return a.concat(x); });
// => [2, 3, 13, 4, 14, 5, 15, 25, 35]

reduce sets the accumulator to the first element (or a starting value if provided), then calls the function with the accumulator and each successive element. The function we provide is concatenation. If we say input is [a, b, c], then the above command will be equivalent to a.concat(b).concat(c). [concat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat) produces a new array by smushing two or more arrays together.

EDIT: Actually, there is another possible answer:

Array.prototype.concat.apply(input[0], array.slice(1));
// => [2, 3, 13, 4, 14, 5, 15, 25, 35]

This directly calls concat with multiple arguments; if input is again [a, b, c], then this is equivalent to a.concat(b, c). apply calls a function with a given receiver and arguments; slice will give us just a part of the array, in this case everything starting from the first element (which we need to chop off since it needs to be the receiver of the concat call).

I am quiet sure this is best answer among all other answers, but... A nice little explanation will help others understand what is happening.. :) — Rayon, May 23 '16 at 07:10

score 2 · Answer 2 · answered May 23 '16 at 07:05

2

One liner would be

input = [[2],[3,13],[4,14],[5,15,25,35]];
[].concat.apply([],input);

answered May 23 '16 at 07:05

Jagdish Idhate

7,513
9
35
51

score 1 · Answer 3 · answered May 23 '16 at 06:58

1

You can use lodash's flattenDeep()

_.flattenDeep([1, [2, [3, [4]], 5]]);
// → [1, 2, 3, 4, 5]

answered May 23 '16 at 06:58

fhollste

785
6
16

score 1 · Answer 4 · answered May 23 '16 at 06:59

User concat.check this for more information http://www.w3schools.com/jsref/jsref_concat_array.asp

var input=[[2],[3,13],[4,14],[5,15,25,35]];
var output=[];
for(var i = 0; i < input.length; i++)
{
  output = output.concat(input[i]);
}
console.log(output);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

score 1 · Answer 5 · answered May 23 '16 at 06:59

use concat is the perfect way

The concat() method is used to join two or more arrays. This method does not change the existing arrays, but returns a new array, containing the values of the joined arrays.

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

console.log(newArr);

Reducing array of items into a single array list

5 Answers5