Is there an easy way to make nested array flat?

Question

That is to make this:

[ [\'dog\',\'cat\', [\'chicken\', \'bear\'] ],[\'mouse\',\'horse\'] ]

into:

[\'dog\',\'cat\',\'chicken\',\'

Answer 1

The easiest way of flattening the Objects of any depth would be using the flat method

var arr = [['dog','cat', ['chicken', 'bear']],[['mouse','horse'],'lion'] ]; 
var flattened = arr.flat(Infinity);
//output--> ["dog", "cat", "chicken", "bear", "mouse", "horse", "lion"]

More aout Flat()

Answer 2

Now in 2019 you can easily use Array.flat with whatever depth you want.

let arr  = [ ['dog','cat', ['chicken', 'bear'] ],['mouse','horse'] ]

let op = arr.flat(Infinity)

console.log(op)

Now if you want to get unique values you can combine both Set and flat

let arr  = [ ['dog','cat', ['chicken', 'bear', 'cat'] ],['mouse','horse', 'dog'], [[[['deeper','chicken']]]] ]

let unique  = [...new Set(arr.flat(Infinity))]

console.log(unique)

Browser comparability Except IE all other seems to support for IE you can use polyfill.

Answer 3

What about this one liner code ?

console.log([['dog', 'cat', ['chicken', 'bear']], [['mouse', 'horse'], 'lion']].join().split(','));

basically join will make comma separated string from nested array and using split you can get 1d array, nice ? bonus it'll work on all major browsers as well :)

Answer 4

In modern browsers you can do this without any external libraries in a few lines:

Array.prototype.flatten = function() {
  return this.reduce(function(prev, cur) {
    var more = [].concat(cur).some(Array.isArray);
    return prev.concat(more ? cur.flatten() : cur);
  },[]);
};

console.log([['dog','cat',['chicken', 'bear']],['mouse','horse']].flatten());
//^ ["dog", "cat", "chicken", "bear", "mouse", "horse"]

Answer 5

Small fix for ChewOnThis_Trident solution and it works perfect:

Array.prototype.flatten = function() {
    return this.reduce(function(a, b) {
        return a.concat(b);
    }, []);
};

Answer 6

Grab underscore.js and use the flatten function.

_.flatten([ ['dog','cat', ['chicken', 'bear'] ],['mouse','horse'] ]);