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All topics›JavaScript›Basic recursion

Flatten a Deeply Nested Array

beginnerlayer B10 · Basic recursion5 tests

Given an array whose elements may themselves be arrays, to any depth, return a flat array of all the non-array values in order.

  • You may not use Array.prototype.flat or flatMap — write the recursion yourself
  • The depth is arbitrary and unknown in advance
  • Nested empty arrays contribute nothing: [[], [[]]] flattens to []
  • Values of any type are kept as-is, including 0, false and null — only arrays are unwrapped

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