Get union of arrays

Merge arrays and keep each value once, in first-seen order.

JavaScript Version 1.0.0 · MIT · .md

function union(arrays) { return [...new Set(arrays.flat())]; }

Input & expected output

[
  [
    "[email protected]",
    "[email protected]"
  ],
  [
    "[email protected]",
    "[email protected]"
  ]
]

[
  "[email protected]",
  "[email protected]",
  "[email protected]"
]

The edge case

[]

[]

Know the limits

• The original took the arrays as separate arguments; the lab passes one array of arrays.
• Values compare with SameValueZero.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Clone an array — Create a new array without copying the objects inside it.
• Remove duplicate values — Keep the first occurrence of each value, in its original order.
• Flatten a nested array — Turn a nested array into one sequence of values.