Javascript:Flatten Array to single depth

Sample Input:

const numbers = [

1,

[3, [2, 8, [12, 9]]],

[5],

[12, [[5]]],

[100, [23, 45]]

]

Sample Output:

const numnbers = [

1, 3, 2, 8, 12,

9, 5, 12, 5, 100,

23, 45

]

Solution(1st Method):

const numbers = [

1,

[3, [2, 8, [12, 9]]],

[5],

[12, [[5]]],

[100, [23, 45]]

]

function flattenNextedArray(arr) {

let numbers = [];

for (let elt of arr) {

if (Array.isArray(elt)) {

numbers = numbers.concat(flattenNextedArray(elt))

} else {

numbers.push(elt)

}

}

return numbers

}

var flatten = flattenNextedArray(numbers)

console.log(flatten)

Solution(2nd Method):

const numbers = [

1,

[3, [2, 8, [12, 9]]],

[5],

[12, [[5]]],

[100, [23, 45]]

]

var flatten = numbers.flat(Infinity)

console.log(flatten)