8 Free Array Tools That Replace Boilerplate Code You Shouldn’t Be Writing
The moment you copy a utility function for the third time, you’ve admitted it belongs in a library — not in your project. chunk(), unique(), groupBy(). These exist because the problem is universal. So why are you still rewriting them?
These eight tools are free, browser-based, and do exactly those operations — no install, no import, no version drift six months from now.
1. Chunk Array — Split Arrays into Batches
When you need to process 10,000 records but your API only accepts 100 at a time, you need chunking. The logic is trivial. The edge cases aren’t.
What it does: Splits any array into sub-arrays of a specified size.
Example: [1, 2, 3, 4, 5, 6] with size 2 → [[1, 2], [3, 4], [5, 6]]
Why it matters: Batch processing keeps memory predictable and API calls retryable. Every data pipeline eventually needs this. There’s no reason to write it more than once — and with this tool, you don’t have to.
2. Uniq Array — Remove Duplicates Without Writing a Filter
Your solution is probably [...new Set(array)]. That works. But explaining it in a code review, documenting it for a teammate, or handling nested objects takes more code. A dedicated tool does it cleanly and gives you shareable output.
What it does: Removes duplicate values from a JSON array, keeping the first occurrence of each.
Example: ["a", "b", "a", "c"] → ["a", "b", "c"]
Why it matters: Deduplication is in data pipelines, user input sanitization, and API response normalization. You need it constantly; you don’t need to maintain the code for it.
3. Difference Arrays — Find What One Array Has That Others Don’t
You have all users and paid users. You need unpaid users. That’s set difference — and it’s a line of code you could write, or a tool you could open in 10 seconds.
What it does: Returns values from the source array that don’t appear in any of the exclude arrays. Supports case-insensitive comparison for strings and multiple exclude arrays.
Example: [1, 2, 3, 4] minus [2, 3] → [1, 4]
Why it matters: Permission systems, tag filtering, content moderation pipelines, CRM cleanup. All of them need this operation. None of them need you to debug a custom implementation.
4. Drop Items — Remove First N Elements Cleanly
Skip the header row. Remove the first configuration entry. Start processing from index N. These sound trivial. Then you test n=0, n larger than the array, and empty arrays — and suddenly it’s 20 lines.
What it does: Removes the first N items from the start of an array.
Example: [1, 2, 3, 4, 5] drop 2 → [3, 4, 5]
Why it matters: array.slice(n) covers most cases, but the edge cases are where bugs live. This tool handles them all and outputs metadata showing what was dropped.
5. Flatten Array — One Level of Nesting, Exactly
Your API returns [["a", "b"], ["c", "d"]] but you need ["a", "b", "c", "d"]. Full recursive flatten would destroy your structure. You need exactly one level.
What it does: Flattens a nested array exactly one level deep.
Example: [1, [2, [3]], 4] → [1, 2, [3], 4]
Why it matters: One-level flatten covers 90% of real-world cases without going too deep. This tool gives you that — and nothing more. That’s exactly what you want.
6. Fill Array — Generate Placeholder Arrays Instantly
You need 50 slots, each containing "pending". Or a boolean array initialized to false. You’re writing a loop that will sit in your codebase for two years before someone asks what it does.
What it does: Fills an array (or a slice of it) with a specified value. Handles typed values — booleans, numbers, null — not just strings.
Example: Fill positions 1–3 of [1, 2, 3, 4, 5] with "" → [1, "", "", "", 5]
Why it matters: Test data, form state scaffolding, UI placeholders. The operation takes seconds. Writing the loop takes longer and carries a maintenance burden you don’t need.
7. Group By — Organize Arrays by Property Without reduce()
You have transactions and need them grouped by category. Orders by status. You’re probably writing a reduce() with an object accumulator — and it works, but it’s not obvious to the next person reading it.
What it does: Groups a collection by a property name or path.
Example: [{type:"a"}, {type:"b"}, {type:"a"}] grouped by type → {a: [{type:"a"}, {type:"a"}], b: [{type:"b"}]}
Why it matters: _.groupBy is lodash’s most-used function for a reason. This tool gives you the operation without the import statement — and the result is cleaner to read in code reviews.
8. Zip Arrays — Combine Arrays by Index
Names and scores. Form fields and labels. CSV columns that should have been paired from the start. Zip handles it.
What it does: Groups elements at the same index from multiple arrays into a single array. Handles 2–4 arrays; missing positions become null.
Example: ["a", "b"] + [1, 2] → [["a", 1], ["b", 2]]
Why it matters: Spreadsheet transformations, form field pairing, any data alignment by position. You could write the length-checking logic yourself, or you could open a URL.
Utility functions don’t die. They get copied from project to project, accumulating minor modifications each time, until nobody knows which version is the canonical one or whether the original had a reason for existing. These eight tools cover the most commonly copied array operations. Bookmark them, share the URLs with your team, and stop starting every project with last project’s utilities folder.
