Enumerate a list with indexes

Enumerate List with Index turns an ordered array of strings into clear, referenceable labels. Choose whether counting begins at zero or one, provide any short separator, and receive both an array of formatted entries and a newline-joined text version. The original item order and text are preserved exactly; only the index and separator are added. This is useful when application code, documentation, review notes, prompts, or exported data need stable labels that people and systems can quote without ambiguity.

Choose the index convention that matches your audience

Start by deciding whether the first label should be zero or one. Zero-based indexing is the natural choice when the result will be compared with array positions in JavaScript, Python, or many other programming environments. It lets a displayed label correspond directly to the position a developer would use in code.

One-based indexing is usually easier for readers in instructions, agendas, checklists, survey choices, and editorial review because the first visible entry is conventionally called item one. The capability does not sort, filter, trim, or deduplicate the supplied values. It walks the array once in its existing order, which means repeated strings remain separate entries and blank strings still receive indexes.

This preservation is important when position carries meaning. If your source data is generated elsewhere, clean or reorder it before calling this operation, then treat the returned labels as a faithful positional view of that prepared list.

Use a separator that makes each label readable

The separator is inserted literally between the computed index and each original item. The default is a colon followed by a space, producing labels such as <code>0: red</code>. You can instead use a period and space for familiar numbered-list styling, a closing parenthesis for compact answer choices, a tab for downstream table processing, or a visible token such as an arrow when the output is meant for logs.

Because the string is used exactly as supplied, whitespace is significant: a colon without a trailing space produces <code>0:red</code>, while a colon with one space produces <code>0: red</code>. Empty separators are also valid when compact identifiers are desired, although a visible boundary is generally easier to interpret. Separators are limited to 32 characters to keep the operation focused on labeling rather than templating.

Item strings are never parsed for existing numbers or punctuation. If an item already begins with a number, that content remains untouched after the new index prefix, so callers should remove old labels first when replacement rather than composition is intended.

Integrate the structured and text results safely

The response includes <code>enumerated</code>, an array containing one formatted string for every input item, and <code>text</code>, the same strings joined with newline characters. Use the array when another program will map, filter, serialize, or display entries independently. Use the text form when writing a plain-text block, preparing a message, creating a prompt section, or copying the result into documentation.

The response also reports the count, selected index base, and separator, making the formatting decision explicit for auditing and debugging. Validation rejects missing or empty arrays, non-string members, unsupported index bases, oversized collections, oversized items, and overly long separators. Those checks keep malformed data from being partially transformed.