join

join(array, separator) → string · String

Join array elements into a single string with a separator. This is the string join — for data restructuring (nesting children under parents), see nestBy() in Chapter 20.

array (required): array of values to join (non-strings are converted automatically)
separator (required): string to insert between elements

bash

echo '{"tags": ["urgent", "billing", "review"]}' | utlx -e 'join($input.tags, ", ")'
# urgent, billing, review

utlx

{
  label: join($input.tags, " | "),
  csvLine: join([$input.name, toString($input.age), $input.city], ";"),
  path: join(["usr", "local", "bin"], "/")
}

Anti-pattern: reduce(arr, "", (acc, x) -> concat(acc, x, ", ")) — creates N intermediate strings. join() builds the result in one pass.

join ​

join