As we know, to flatten the array [[0, 1], [2, 3], [4, 5]] by using the method reduce()
var flattened = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
return a.concat(b);
});
So how to flatten this array [[[0], [1]], [[2], [3]], [[4], [5]]] to [0, 1, 2, 3, 4, 5]?
This is an alternative to recursion (see jsfiddle here) and should accept any level of depth which avoids stack overflow.
var array = [[0, 1], [2, 3], [4, 5, [6, 7, [8, [9, 10]]]]];
console.log(flatten(array), array); // does not mutate array
console.log(flatten(array, true), array); // array is now empty
// This is done in a linear time O(n) without recursion
// memory complexity is O(1) or O(n) if mutable param is set to false
function flatten(array, mutable) {
var toString = Object.prototype.toString;
var arrayTypeStr = '[object Array]';
var result = [];
var nodes = (mutable && array) || array.slice();
var node;
if (!array.length) {
return result;
}
node = nodes.pop();
do {
if (toString.call(node) === arrayTypeStr) {
nodes.push.apply(nodes, node);
} else {
result.push(node);
}
} while (nodes.length && (node = nodes.pop()) !== undefined);
result.reverse(); // we reverse result to restore the original order
return result;
}
