read-modify-write
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Node module for reading, modifying and writing files recursively
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Markdown
NodeJS - Read File, Modify Content, Write to File
1. Introduction to read-modify-write
2. Read File/Directory
3. Write to File/Directory
4. Filter files
5. Modify Content
6. Prepare for Production
7. Run tests
This Node module provides an API to interact with the file system and perform recursive sequential IO operations (such as file reading/writing and file content modification). It executes all operations in a blocking and synchronous way. It is a very simple yet very flexible toolkit with size of less than 2KB and no dependencies.
To use the library all we need is to import read-modify-write module into our code.
```js
const rmw = require('read-modify-write');
```
To read file content recursively in a chosen directory we simply need to pass the folder path as the first parameter to the already imported module:
```js
rmw('src/dummy');
```
To copy files from one directory to another we need a path modifier function which is passed as a second parameter:
```js
const move = filePath => filePath.replace('src', 'dist');
rmw('src/dummy', move);
```
The path modifier function takes one parameter which is the location / path for each of the listed files. The code above copies all files in the 'src/dummy' folder to the 'dist/dummy'.
To filter files with certain extension we need to supply a function that will be called on each files on the list, and only return the values that pass a specific test (in this case the file extension is present in the string):
```js
const move = filePath => filePath.replace('src', 'dist');
const filterHtml = c => c.endsWith('.html');
rmw('src/dummy', move, filterHtml);
```
This function, in combination with the previous one can be used to add suffix for certain file types:
```js
const move = filePath => filePath.replace('.js', '.min.js');
const filterJs = c => c.endsWith('.js');
rmw('src/dummy', move, filterJs);
```
Consider an html file in 'src' folder with the following content:
```html
<html lang="en"><head><meta charset="utf-8"><title></title></head></html>
```
To update the file content and save it to a new location we need to pass a forth parameter which is an update function which accepts file content as an argument.
```js
const move = filePath => filePath.replace('src', 'dist');
const filterHtml = c => c.endsWith('.html');
const update = c => c.replace('<title></title>', '<title>Page title</title>');
rmw('src/dummy', move, filterHtml, update);
```
The code above will result in a new html file created in the 'dist/dummy' folder with the following content:
```html
<html lang="en"><head><meta charset="utf-8"><title></title></head></html>
```
This toolkit can assist you automate painful or time-consuming tasks in your development workflow. For example when publishing to production it can help you by doing CSS preprocessing, JS transpiling, minification, and much more:
```js
const terser = require('terser');
const cleanCss = require('clean-css');
const uglify = c => terser.minify(c).then(({ code }) => code);
const clean = c => new cleanCss().minify(c).styles;
const move = filePath => filePath.replace('src', 'dist');
const filterJs = c => c.endsWith('.js');
const filterCss = c => c.endsWith('.css');
rmw('src', move);s
rmw('src/dummy', move, filterJs, uglify);
rmw('src/dummy', move, filterCss, clean);
```
Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can run the tests the following command:
```sh
$ npm test
```