JS Built-ins
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ArrayArray.prototype.flatMapadvanced

Array.prototype.flatMap() — compact strings

📖 Usage Example
const strs = ['hello', '', 'world', '']
strs.flatMap(s => s ? [s.trim()] : [])
// → ['hello', 'world']

Use flatMap() to simultaneously trim, filter out empty strings, and flatten results.

Array.prototype.flatMap() — trim and filter

flatMap() can both transform and filter in one pass. Trimming strings and removing empty ones is a clean use case.

Challenge: Implement compactMap(arr) that trims each string and removes empty strings using flatMap.

compactMap(['  hello  ', '', '  world  ', '   ']) // → ['hello', 'world']
compactMap(['', '  '])                             // → []
💡 Hints (2)
  • • `s.trim()` removes leading/trailing whitespace.
  • • Return `[trimmed]` to keep or `[]` to discard — `flatMap` handles the flattening.