Package Manager

npm

yarn

pnpm

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pnpm exec jest

Semver

Semantic Versioning

MAJOR.MINOR.PATCH-PRE-RELEASE

• MAJOR - incompatible API changes
• MINOR - add/change functionality in a backwards compatible manner
• PATCH - backwards compatible bug fixes
• PRE-RELEASE - a series of dot separated identifiers ([0-9A-Za-z-])

Tilde Ranges

• Allows patch-level changes if a minor version is specified.
• Allows minor-level changes if not.

~1.2.3: >=1.2.3 and <1.3.0
~1: 1.x

Caret Ranges

Allows changes that do not modify the left-most non-zero element in the [major, minor, patch] tuple.

• ^1.2.3 := >=1.2.3 and <2.0.0
• ^0.2.3 := >=0.2.3 and <0.3.0
• ^0.0.3 := >=0.0.3 and <0.0.4

https://semver.org/
https://github.com/npm/node-semver

Spec

Major version zero (0.y.z) is for initial development. Anything MAY change at any time. The public API SHOULD NOT be considered stable.

Patch version MUST be reset to 0 when minor version is incremented.

Patch and minor versions MUST be reset to 0 when major version is incremented.

Precedence

When major, minor, and patch are equal, a pre-release version has lower precedence than a normal version:

Example: 1.0.0-alpha < 1.0.0.

ES6 import

node >= 13

save file as .mjs

Add { "type": "module" } in the package.json

Process

cwd() - the current working directory

child_process

The child_process module provides the ability to spawn subprocesses in a manner that is similar, but not identical, to popen(3). This capability is primarily provided by the child_process.spawn() function:

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const { spawn } = require('child_process');
const ls = spawn('ls', ['-lh', '/usr']);

ls.stdout.on('data', (data) => {
  console.log(`stdout: ${data}`);
});

ls.stderr.on('data', (data) => {
  console.error(`stderr: ${data}`);
});

ls.on('close', (code) => {
  console.log(`child process exited with code ${code}`);
});

Readline

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const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question('What do you think of Node.js? ', (answer) => {
  console.log(`Thank you for your valuable feedback: ${answer}`);
  rl.close();
});

Util

util.deprecate() - wraps fn in such a way that it is marked as deprecated.

fs

fs-extra

fs-extra adds file system methods that aren’t included in the native fs module and adds promise support to the fs methods. It also uses graceful-fs to prevent EMFILE errors. It should be a drop in replacement for fs.

https://github.com/jprichardson/node-fs-extra

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// ES6 version using asynchronous iterators, compatible with node v10.0+

const fs = require("fs");
const path = require("path");

async function* walk(dir) {
    for await (const d of await fs.promises.opendir(dir)) {
        const entry = path.join(dir, d.name);
        if (d.isDirectory()) yield* walk(entry);
        else if (d.isFile()) yield entry;
    }
}

// Then, use it with a simple async for loop
async function main() {
    for await (const p of walk('/tmp/'))
        console.log(p)
}

Tools

nodemon

ts-node

ts-node-dev