Example 1: javascript array flatten
// flat(depth),
// depth is optional: how deep a nested array structure
// should be flattened.
// default value of depth is 1
const arr1 = [1, 2, [3, 4]];
arr1.flat();
// [1, 2, 3, 4]
const arr2 = [1, 2, [3, 4, [5, 6]]];
arr2.flat();
// [1, 2, 3, 4, [5, 6]]
const arr3 = [1, 2, [3, 4, [5, 6]]];
arr3.flat(2);
// [1, 2, 3, 4, 5, 6]
const arr4 = [1, 2, [3, 4, [5, 6, [7, 8, [9, 10]]]]];
arr4.flat(Infinity);
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Example 2: flatten nested array javascript
// using recursion, .reduce() and .concat() methods
// works with arrays of any depth
function flatten(arr)
{
return arr.reduce((acc, cur) => acc.concat(Array.isArray(cur) ? flatten(cur) : cur), []);
};
const arr = [[1,2],[3,[4,[5]]]];
const flattened = flatten(arr);
console.log(flattened);
/*
Output: [ 1, 2, 3, 4, 5 ]
*/
Example 3: array flatten
const arr = [1, 2, [3, 4]];
// To flat single level array
arr.flat();
// is equivalent to
arr.reduce((acc, val) => acc.concat(val), []);
// [1, 2, 3, 4]
// or with decomposition syntax
const flattened = arr => [].concat(...arr);