How to flatten a (nested) array

JavaScript, algorithms, arrays

Here are two approaches you might take to flattening a nested array. One approach is recursive and the other approach is iterative.

flattenArrayTry in REPL
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function recursiveFlatten(array) {
  return array.reduce((accumulator, element) => {
    return Array.isArray(element) ? [...accumulator, ...recursiveFlatten(element)] : [...accumulator, element];
  }, []);
}
function iterativeFlatten(array) {
    const stack = [...array];
    const result = [];
    
    while (stack.length) {
        const next = stack.pop();
        
        if (Array.isArray(next)) {
            stack.push(...next);
        } else {
            result.push(next);
        }
    }
    
    return result.reverse();
}