This document discusses jscpd, a copy/paste detector for JavaScript source code. It describes the reasons for its creation, its algorithm based on Rabin Karp string matching, and its architecture which uses parsers like Esprima to tokenize code into structured tokens. The tool supports various languages and outputs reports on copy/paste detections in JSON, XML, and other formats. Future plans include additional reporters, cross-project detections, and performance improvements.

1. Copy/Paste detector
for source code on
JavaScript
Andrey Kucherenko
Lead Software Engineer @ EPAM Systems (Kiev)

2. ABOUT
Andrey Kucherenko
Lead Software Engineer @ EPAM Systems (Kiev)
https://github.com/kucherenko/jscpd

3. ABOUT TOPIC
Copy/Paste detector for source code on
JavaScript
● Reasons
● Algorithm
● Architecture
● Tools
● Plans
https://github.com/kucherenko/jscpd

4. REASONS
https://github.com/kucherenko/jscpd

5. EXISTING TOOLS
https://github.com/kucherenko/jscpd
PHPCPD

6. ALGORITHM
Rabin Karp: String Matching
Algorithm
https://github.com/kucherenko/jscpd

7. ALGORIHTM
https://github.com/kucherenko/jscpd

8. ALGORIHTM
https://github.com/kucherenko/jscpd
const answer = 6 * 7;
const click = event => console.log(event)
function hello(name) {
console.log(`Hello ${name}`);
}

9. ALGORIHTM
https://github.com/kucherenko/jscpd
{ "type": "Keyword", "value": "const" },
{ "type": "Identifier", "value": "answer" },
{ "type": "Punctuator", "value": "=" },
{ "type": "Numeric", "value": "6" },
{ "type": "Punctuator", "value": "*" },
{ "type": "Numeric", "value": "7" },
{ "type": "Punctuator", "value": ";" },
{ "type": "Keyword", "value": "const" },
{ "type": "Identifier", "value": "click" },
{ "type": "Punctuator", "value": "=" },
{ "type": "Identifier", "value": "event" },
{ "type": "Punctuator", "value": "=>" },
{ "type": "Identifier", "value": "console" },
{ "type": "Punctuator", "value": "." },
{ "type": "Identifier", "value": "log" },
{ "type": "Punctuator", "value": "(" },
{ "type": "Identifier", "value": "event" },
{ "type": "Punctuator", "value": ")" },
{ "type": "Keyword", "value": "function" },
{ "type": "Identifier", "value": "hello" },
{ "type": "Punctuator", "value": "(" },
{ "type": "Identifier", "value": "name" },
{ "type": "Punctuator", "value": ")" },
{ "type": "Punctuator", "value": "{ " },
{ "type": "Identifier", "value": "console" },
{ "type": "Punctuator", "value": "." },
{ "type": "Identifier", "value": "log" },
{ "type": "Punctuator", "value": "(" },
{ "type": "Template", "value": "`Hello ${ " },
{ "type": "Identifier", "value": "name" },
{ "type": "Template", "value": " }`" },
{ "type": "Punctuator", "value": ")" },
{ "type": "Punctuator", "value": ";" },
{ "type": "Punctuator", "value": " }"

10. ALGORIHTM
https://github.com/kucherenko/jscpd
'3237124366', '07c4845853', '0b70d4ffe0', '7bb34abce5',
'59fb864552', '9f769a5e93', 'c913cc056b', '3237124366',
'4b09c07aa1', '0b70d4ffe0', '06b9bc0ef4', 'caf867a125',
'bd6845a7e7', '7fb7e4e540', '5fb26ad7b9', '66e5a4ee55',
'06b9bc0ef4', '3aa73104c6', '4a43a19740', 'bca573934e',
'66e5a4ee55', 'da5400f4e2', '3aa73104c6', 'fecd1071ce',
'bd6845a7e7', '7fb7e4e540', '5fb26ad7b9', '66e5a4ee55',
'4ab7ca70d5', 'da5400f4e2', '7c61a943f3', '3aa73104c6',
'c913cc056b', 'a120515c8c'

11. ARCHITECTURE
https://github.com/kucherenko/jscpd

12. TOKENS
https://github.com/kucherenko/jscpd
Esprima
acorn

13. TOKENS
https://github.com/kucherenko/jscpd

14. TOOLS
https://github.com/kucherenko/jscpd

15. SUPPORTED LANGUAGES
https://github.com/kucherenko/jscpd
JavaScript Go Swift
CoffeeScript Python Objective-C
TypeScript CSS/SASS Perl
Java C# Lua
C/C++ HTML Scala
PHP XML/XSLT Other…

16. FEATURES
● Reporters: json, xml, xslt, console
● Blame authors of copy/paste
● Use semantic of the languages (e.g. skip
comments)
● Community extensions: gulp-jscpd, html-
reporter, grunt-jscpd, etc.
https://github.com/kucherenko/jscpd

17. STATISTICS
https://github.com/kucherenko/jscpd

18. REPORTS
https://github.com/kucherenko/jscpd

19. REPORTS
https://github.com/kucherenko/jscpd

20. REPORTS
https://github.com/kucherenko/jscpd

21. PLANS
● More reporters
● Cross projects detections
● New API
● Improve performance (add cache, add
bloom filters, etc)
● Persistent store (NoSQL etc.)
● Reports for period
https://github.com/kucherenko/jscpd

22. QUESTIONS
Questions?
https://github.com/kucherenko/jscpd
Questions?
Questions?