Intersperse element between elements

Insert a separator between every pair of items.

JavaScript Version 1.0.0 · MIT · .md

function intersperse({ values, separator }) { return values.flatMap((value, i) => (i === 0 ? [value] : [separator, value])); }

Input & expected output

{
  "values": [
    "ana",
    "rui",
    "lia"
  ],
  "separator": ","
}

[
  "ana",
  ",",
  "rui",
  ",",
  "lia"
]

The edge case

{
  "values": [],
  "separator": ","
}

[]

Know the limits

• The original built Array(2n − 1), which throws for an empty array; flatMap returns [].

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.