How to Convert a CSV File to a JavaScript Array Without Duplicates Using ArrayCat

Updated

ArrayCat converts a list of data or any string into an array, and it can strip duplicate elements during the same pass. To turn a CSV file into a duplicate-free JavaScript array, load or paste your CSV, set the input format to comma separated, choose JavaScript array as the output format, enable Remove duplicate elements, then generate and copy the result. This works when your data is a flat list — one record per row — rather than nested or multi-column records that need to stay grouped.

What ArrayCat accepts as input

ArrayCat reads your data as a list, so the input format you pick tells it how to split rows into individual items. The supported input formats are:

  • One item per row
  • Comma separated
  • Inside quotation marks
  • One item per row, tab separated

For a CSV file, comma separated is the format you want. You can either paste the data directly or use the Load file option to bring in a CSV from your machine.

The page notes a Maximum row length, so extremely long single rows may be truncated — keep individual records reasonably short if you notice missing data.

Step-by-step: CSV to a deduplicated JavaScript array

  1. Load or paste your CSV. Use Load file to select the CSV, or paste the comma-separated text into the input area.
  2. Set the input format to "Comma separated." This tells ArrayCat to treat each comma-delimited value as one item.
  3. Set the output format to "JavaScript array." ArrayCat also supports Delphi, Go, Pascal, PHP, Python arrays and SQL insert output, so make sure JavaScript is selected.
  4. Enable the "Remove duplicate elements" transform. This is the step that eliminates repeated values.
  5. Generate the output. ArrayCat applies the selected transforms and produces the array.
  6. Copy the result using the Copy to clipboard button.

The expected result is a JavaScript array literal containing each unique value from your CSV exactly once.

Useful transforms to combine with deduplication

Deduplication rarely happens in isolation — CSV exports often carry messy whitespace or inconsistent casing that makes "duplicates" look different. ArrayCat's transform list includes options that pair well with removing duplicates:

Transform Why you'd add it
Trim whitespace Removes leading/trailing spaces so "apple" and "apple " match as duplicates
Unify whitespace Collapses internal spacing differences
Strip excess whitespace Cleans up irregular spacing
Convert to lower case Makes Apple and apple count as the same value
Remove empty elements Drops blank rows common in CSV exports
Sort elements Orders the final array for easier reading
Remove trailing separators Cleans up dangling commas before conversion

If your CSV has a trailing comma on each line, Remove trailing separators plus Remove empty elements prevents phantom blank entries from surviving into the array.

Common snags

  • Duplicates survive because of whitespace or case. Enable Trim whitespace and Convert to lower case before deduplication so near-identical values collapse correctly.
  • Blank entries appear in the array. CSV files often end with a newline or trailing comma; turn on Remove empty elements and Remove trailing separators.
  • Wrong output language. If you get a PHP or Python array instead of JavaScript, recheck the output format selection.
  • Quoted fields with commas inside. If your CSV wraps values in quotes, try the Inside quotation marks input format so embedded commas don't split a single value into two.

ArrayCat is described as a free tool, and it handles the conversion entirely through the format and transform options above — no scripting required.