Remove duplicate values

Keep the first occurrence of each value, in its original order.

JavaScript Version 1.0.0 · MIT · .md

function unique(values) { return [...new Set(values)]; }

Input & expected output

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

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

The edge case

[
  {
    "id": 1
  },
  {
    "id": 1
  }
]

[
  {
    "id": 1
  },
  {
    "id": 1
  }
]

Know the limits

• Set compares objects by reference. Two separately created objects are not duplicates.
• Values use SameValueZero equality; this is not deep deduplication.

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.
• Flatten a nested array — Turn a nested array into one sequence of values.
• Split an array into chunks — Build consecutive chunks without changing the original array.