psenger

/**
 * Problem: an array of data, that has an array of sub data.
 * Three ways to do this:
 *  - map+split, reduce, push+spread, sort ( side effect: order is not retained )
 *  - map+split, flat
 *  - flatMap+split
 */
const values = 'a|b|c|d,e|f,g|h|i|j|k|l'

const A = values.split(',').map((v)=>v.split('|')).reduce((acc,v)=>{

psenger

Apache Installation

yum install httpd -y

Default install directory /var/www/html

Apache Starting

psenger

Curry

Currying is the process of turning a function that expects multiple parameters into one that, when supplied fewer parameters, returns a new function that awaits the remaining ones. [1]

---

[1] https://fr.umio.us/favoring-curry/

psenger

const pattern = 'abcdefgh';

for (const [currentChar, nextChar] of pattern.split('').reduce((acc,value,idx,arr)=>{const entry = [value]; if ( arr.length > idx + 1 ) entry.push(arr[idx+1]); acc.push(entry); return acc},[])) {
    console.log(currentChar,nextChar)
}
/**
a b
b c
c d
d e

psenger

 
const {readFile} = require("fs").promises;
const run = async () => {
    const loadCSV = async (fileName ) => {
        const contents = await readFile(fileName, 'utf8');
        const lines = contents
            .split('\n')
            .filter(Boolean)
            .map((t)=>t.trim()) // remove leading and trailing \r for non-utf8 files
            .map((line)=>{

psenger

How to split a file on lines

Use case, you have a csv file, you want it to be split by 100 line numbers into files.. The onlys ide effect is you get sample-aa, sample-ab.... no extension

split -l 100 sample.csv sample-

psenger

const AWS = require('aws-sdk')
const fs = require("fs").promises;
const {join} = require('path')
const path = require("path");
const { createReadStream, createHash } = require('crypto')

const credentials = {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID || 'test',
    secretAccessKey: process.env.AWS_SECRET_KEY || 'test' ,
}

psenger

git diff --name-only HEAD

psenger

In Node.js, the process.exit() method is used to exit the current Node.js process with a given exit code. The number argument passed to process.exit() represents the exit code that the Node.js process will exit with.

Here are the commonly used exit codes and their meanings:

• 0: The process exits successfully without any errors.
• 1: The process exits due to an uncaught exception.
• 2: The process exits due to a misconfiguration or missing file.
• 3: The process exits due to a fatal error.

psenger

Process NextTick and SetImmediate

In Node.js, process.nextTick() is a method that allows you to schedule a function to be executed on the next iteration of the event loop. It is often used to defer the execution of a function until after the current function has completed.

The process.nextTick() method is similar to setImmediate(), but with a few key differences. While setImmediate() schedules a callback to run in the next iteration of the event loop, process.nextTick() schedules a callback to run at the end of the current iteration of the event loop, before any I/O operations.

Here is an example of how process.nextTick() can be used:

console.log('start');