Merge two arrays

Concatenate two arrays, optionally dropping duplicates.

JavaScript Version 1.0.0 · MIT · .md

function merge({ a, b, unique = false }) { return unique ? [...new Set([...a, ...b])] : [...a, ...b]; }

Input & expected output

{
  "a": [
    "[email protected]"
  ],
  "b": [
    "[email protected]",
    "[email protected]"
  ]
}

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

The edge case

{
  "a": [
    "[email protected]"
  ],
  "b": [
    "[email protected]",
    "[email protected]"
  ],
  "unique": true
}

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

Know the limits

• The original page showed both versions; unique selects one.

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.