How Does Order-Preserving Line Deduplication Work?
The deduplicator iterates through each line from top to bottom using a JavaScript Set, keeping the first occurrence of every unique line and discarding subsequent duplicates without reordering your list.
When working with keyword lists, data exports, log files, or email directories, duplicate entries cause bloat and processing errors. Text Cleaner removes duplicate lines instantly while strictly preserving the first appearance of each unique item.
What Algorithm & Complexity Rule Does Deduplication Use?
The algorithm runs const seen = new Set(); lines.filter(line => !seen.has(line) && seen.add(line)), completing in linear O(n) time complexity even on lists with 50,000+ lines.
- Exact Line Matching: Comparisons are exact per line (case-sensitive). Tip: run Trim or lowercase first if your list has inconsistent trailing spaces or casing.
- Worked Before / After Example: Input
apple\nbanana\napple\norange\nbanana\ngrape(6 lines, 6 words, 38 characters) → Outputapple\nbanana\norange\ngrape(4 unique lines, 4 words, 25 characters; 2 duplicate lines removed).
| Deduplication Scenario / Rule | Input Example (Before) | Output Result (After) | Duplicate Lines Removed (count) |
|---|---|---|---|
Order-Preserving Set Filter (Set.has) |
apple\nbanana\napple\norange (4 lines, 25 chars) |
apple\nbanana\norange (3 lines, 19 chars) |
-1 duplicate line (-6 chars) |
| Repeated Log / CSV Entries | id_101\nid_102\nid_101\nid_101 (4 lines, 27 chars) |
id_101\nid_102 (2 lines, 13 chars) |
-2 duplicate lines (-14 chars) |
| Trim Trailing + Dedupe Pipeline | user@acme.com \nuser@acme.com (2 lines, 29 chars) |
user@acme.com (1 line, 13 chars) |
-2 spaces trimmed, -1 duplicate line |
| Dedupe + Sort A–Z Pipeline | zeta\nalpha\nzeta\nbeta (4 lines, 20 chars) |
alpha\nbeta\nzeta (3 lines, 15 chars) |
-1 duplicate removed + sorted A–Z |
How Can You Combine Deduplication with Alphabetical Sorting?
Click Dedupe to strip repeated rows first, then click Sort A–Z or Sort Z–A to alphabetize the remaining unique items.
You can also chain operations: click Dedupe to remove repeated items, and then click Sort A–Z to order your clean list alphabetically.
