I needed to identify common code between 2 folders of the same project.

Instead of checking all the files manually one by one, I used a tool that made the task easier: [jscpd](https://github.com/kucherenko/jscpd "jscpd").

It's an NPM package that you can install in your project, but in my case I used [the CLI version](https://github.com/kucherenko/jscpd/tree/master/packages/jscpd "https://github.com/kucherenko/jscpd/tree/master/packages/jscpd").

If I want to find the code in common between the `./folder1` and `./folder2` folders in my next.js project, want to ignore the code compiled in `./.next` and the `./node_modules`, and want an html report, I position myself at the root of my project, and run the following command:

```bash:Terminal
npx jscpd --skipLocal ./folder1 ./folder2 --reporters html --ignore "**/node_modules,**/.next"
```

Then you just have to open the file `./report/html/index.html` in a browser to see the report.

> Be careful, you must remember to delete the report and not commit it!

![jscpd report screenshot](https://res.cloudinary.com/dm589m8iw/image/upload/v1667330367/mehdi-content/jscpd-screenshot_pwngxe.png "jscpd report screenshot")

## Settings

We can also change the basic parameters according to our needs. The [documentation](https://github.com/kucherenko/jscpd/tree/master/packages/jscpd#options) lists all the options.

For example, if we take the following command line:

```bash:Terminal
npx jscpd --pattern "src/**/*.js" --min-tokens 15 --min-lines 5
```

* `--pattern` or `-p` allows us to target only the files corresponding to a given pattern. Here we will target all javascript files in the `src` folder.
* `--min-tokens` or `-k` is the minimum number of token repetitions. A token is the equivalent of a word. Here, an extract of code will only be detected as duplicated if it has 15 or more identical tokens.
* `--min-lines` or `-l` is the minimum number of lines of code to detect. Here, an extract of code will be detected as duplicated only from 15 identical lines.

***

[Source](https://javascript.plainenglish.io/how-to-detect-duplicate-code-in-a-project-c2a2f9bfdbe0)

A CLI tool to quickly identify duplicate code.