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devexamples

Deep Flatten Nested Arrays Without Recursion

Flatten arbitrarily nested arrays with an explicit stack and optional depth limit, avoiding call-stack overflow on deep input.

JavascriptData Integrity

Code

snippet
export function flattenDeep(input, depth = Infinity) {
  if (!Array.isArray(input)) throw new TypeError("input must be an array");
  if (depth !== Infinity && (!Number.isInteger(depth) || depth < 0)) {
    throw new RangeError("depth must be a non-negative integer or Infinity");
  }
  const output = [];
  const stack = [];
  for (let index = input.length - 1; index >= 0; index -= 1) {
    stack.push({ value: input[index], level: 1 });
  }
  while (stack.length > 0) {
    const entry = stack.pop();
    if (Array.isArray(entry.value) && entry.level <= depth) {
      for (let index = entry.value.length - 1; index >= 0; index -= 1) {
        stack.push({ value: entry.value[index], level: entry.level + 1 });
      }
    } else {
      output.push(entry.value);
    }
  }
  return output;
}

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