[JavaScript] Download base64 encoded file

            const sBase64 = "JVBERi0xLjQKJcOkw7zDtsOfCjIgMCBvYmoKPDwvTGVuZ3....."
            const arrayBuffer = new Uint8Array([...window.atob(sBase64)].map(char => char.charCodeAt(0)))
            const fileLink = document.createElement('a')

            fileLink.href = window.URL.createObjectURL(new Blob([arrayBuffer]))
            fileLink.setAttribute('download', "example.pdf")
            document.body.appendChild(fileLink)
            fileLink.click()

[JavaScript] map an array of objects to return an array of objects

Recently I hat to create an array of objects from another array of objects to change some property names and to enrich it with some values. To iterate over the array I used the map() function. But when trying to return the new object using the brackets {}, the map function instead expects me trying to write a function… Therefore you need to wrap the return object in ()

const aPersons = [{
  id: 1,
  name: 'max'
}, {
  id: 2,
  name: 'peter'
}]

const aResult = aPersons.map(person => ({ value: person.id, text: person.name, someboolean: true }))
console.log(aResult)

[Postman] Visualize base64 image

If you have a service which returns a payload like the following (including a base64 endcoded jpeg) you can view it directly in postman.

{
        "photo": "/9j/4AAQSkZJRgABAgAAAQABAAD/2wBDAAMCAgMCAgMDAwMEAwMEBQgFBQQEBQoHBwYIDAoMDAsK\r\nCwsND..............",
        "photoId": "192",
        "mimeType": "image/jpeg"
}

This can be done with a few lines of code. In Postman navigate to the “Tests” tab:

and insert the following lines:

//output to postman console
console.log("PhotoId: " + pm.response.json()["photoId"]);
console.log("Base64: " + pm.response.json()["photo"]);

//output in visualize tab
let template = `<img src='{{img}}'/>`;

pm.visualizer.set(template, { 
    img: `data:image/jpeg;base64,${pm.response.json()["photo"]}`
});

In the “Visualize” tab you should now find your image

[PDF.js] Prevent loading default pdf

This can be done by appending ?file= to the src path, like it is mentionend here.

<!-- "?file=" prevents loading the default document -->
<iframe id="pdf-js-viewer" src="/pdf/web/viewer.html?file=" title="webviewer" frameborder="0" width="100%" height="700" allowfullscreen="" webkitallowfullscreen=""/>

Or by setting the variable defaultUrl to blank using the onload event.

pdfViewer = document.getElementById("pdf-js-viewer");

pdfViewer.onload = () => {
          pdfViewer.contentWindow.PDFViewerApplicationOptions.set(
            "defaultUrl",
            ""
          );
}; 

[nodejs] read and write a file

https://nodejs.dev/learn/reading-files-with-nodejs

https://nodejs.dev/learn/writing-files-with-nodejs

        const fs = require("fs")

        try {
            // read from local folder
            const localPDF = fs.readFileSync('PDFs/myFile.pdf')

            //write back to local folder
            fs.writeFileSync('PDFs/writtenBack.pdf', localPDF )

        } catch (err) {
            console.error(err)
        }

Converting to Base64

        try {
            // read from local folder
            const localPDF = fs.readFileSync('PDFs/myFile.pdf')
            const localBase64 = localPDF.toString('base64')

            //write back to local folder
            fs.writeFileSync(`PDFs/writtenBack.pdf`, localBase64, {encoding: 'base64'})

        } catch (err) {
            console.error(err)
        }

Reading and writing using streams with pipe

        //read and write local file
        const reader = fs.createReadStream("PDFs/myFile.pdf")
        const writer = fs.createWriteStream('PDFs/writtenBack.pdf');
        reader.pipe(writer)

[ABAP] Convert JavaScript Timestamp to yyyy-MM-dd’T’HH:mm:ss

DATA(lv_js_timestamp) = "/Date(1615161600000)/".

"Extract /Date(1615161600000)/ to 1615161600000
FIND REGEX '([0-9]+)' IN lv_js_timestamp IGNORING CASE SUBMATCHES DATA(js_timestamp).

cl_pco_utility=>convert_java_timestamp_to_abap( EXPORTING iv_timestamp = js_timestamp
                                                IMPORTING ev_date      = DATA(lv_date)
                                                          ev_time      = DATA(lv_time) ).
"2021-03-08T00:00:00
CONVERT DATE lv_date TIME lv_time INTO TIME STAMP DATA(timestamp) TIME ZONE 'UTC'.
rv_datetime = |{ timestamp TIMESTAMP = ISO }|.

[nodejs] APIs and Microservices Projects

These are my notes while doing the course APIs and Microservices on https://www.freecodecamp.org. I highly recommend it if you prefer to try things directly rather than watching videos.


Timestamp Microservice

https://repl.it/@nocin/boilerplate-project-timestamp#server.js

app.get("/api/timestamp/", (req, res) => {
  res.json({ unix: Date.now(), utc: Date() });
});

app.get("/api/timestamp/:date?", (req, res) => {

  //utc date?
  let date = new Date(req.params.date)
  if (date != "Invalid Date") {
   res.json({unix: date.getTime(), utc: date.toUTCString()});
  }

  //unix timestamp?
  const dateInt = parseInt(req.params.date);
  date = new Date(dateInt).toUTCString();
  if (date != "Invalid Date") {
    res.json({unix: dateInt, utc: date});
  }
  
  //invalid input
  res.json({ error: date });
});


Request Header Parser Microservice

https://repl.it/@nocin/boilerplate-project-headerparser#server.js

https://www.npmjs.com/package/express-useragent
https://www.npmjs.com/package/express-request-language

var useragent = require('express-useragent');
var cookieParser = require('cookie-parser');
var requestLanguage = require('express-request-language');

// stuff...

app.use(useragent.express());
app.use(cookieParser());
app.use(requestLanguage({
  languages: ['en-US', 'zh-CN'],
  cookie: {
    name: 'language',
    options: { maxAge: 24*3600*1000 },
    url: '/languages/{language}'
  }
}));

app.get("/api/whoami", (req, res) => {
  res.json({"ipaddress": req.ip,
            "language": req.language,
            "software": req.useragent.source });
});


URL Shortener Microservice

https://repl.it/@nocin/boilerplate-project-urlshortener#server.js

require('dotenv').config();
const express = require('express');
const cors = require('cors');
const app = express();
const bodyParser = require('body-parser');
const dns = require('dns');


// Basic Configuration
const port = process.env.PORT || 3000;

app.use(cors());

app.use('/public', express.static(`${process.cwd()}/public`));

app.get('/', function(req, res) {
  res.sendFile(process.cwd() + '/views/index.html');
});

app.use(bodyParser.urlencoded({extended: false}));

let urls = [];

//POST
app.post("/api/shorturl/new", function(req, res) {
  
  const getHostnameFromRegex = (url) => {
  // run against regex
  const matches = url.match(/^https?\:\/\/([^\/?#]+)(?:[\/?#]|$)/i);
  // extract hostname (will be null if no match is found)
  return matches && matches[1];
  }

  hostname = getHostnameFromRegex(req.body.url);
  console.log("Hostname: " + hostname);

  // if no hostname found, return here
  if (!hostname) res.json({ error: 'invalid url' });

  // check if url is valid
  dns.lookup(hostname, (error, addresses) => {
    console.error(error);
    console.log(addresses);

    if (!error) {
       let newUrl = { original_url : req.body.url, short_url : urls.length + 1};
      urls.push(newUrl);
      res.json(newUrl);
    } else {
      res.json({ error: 'invalid url' });
    }

  });

});

//GET
app.get('/api/shorturl/:num', function(req, res) {

  for (let i = 0; i < urls.length; i++) {
    console.log(urls[i].original_url);
    if (urls[i].short_url == req.params.num) {
        res.redirect(urls[i].original_url);
    }
  }

});

app.listen(port, function() {
  console.log(`Listening on port ${port}`);
});


Exercise Tracker

https://repl.it/@nocin/boilerplate-project-exercisetracker#server.js

const express = require('express')
const app = express()
const cors = require('cors')
require('dotenv').config()
const bodyParser = require('body-parser');
const mongoose = require('mongoose');

app.use(cors())
app.use(express.static('public'))
app.get('/', (req, res) => {
    res.sendFile(__dirname + '/views/index.html')
});


const listener = app.listen(process.env.PORT || 3000, () => {
    console.log('Your app is listening on port ' + listener.address().port)
})


//BodyParser
app.use(bodyParser.urlencoded({ extended: false }));

//DB connect
mongoose.connect(process.env.MONGO_URI, { useNewUrlParser: true, useUnifiedTopology: true });

const { Schema } = mongoose;

//User Schema
const userSchema = new Schema({
    username: { type: String, required: true },
});
const User = mongoose.model("User", userSchema);

//Exercise Schema
const exerciseSchema = new Schema({
    userId: Schema.Types.ObjectId,
    description: { type: String, required: true },
    duration: { type: Number, required: true },
    date: { type: Date, default: Date.now }
});
const Exercise = mongoose.model("Exercise", exerciseSchema);


//POST user to DB
app.post("/api/exercise/new-user", (req, res) => {

    let user = new User({ username: req.body.username });

    user.save((err, data) => {
        //console.log("created User: " + data);
        if (err) return console.error(err);
        res.json({ username: data.username, _id: data._id });
    });

});


//GET all users from DB
app.get("/api/exercise/users", (req, res) => {
    User.find((err, usersFound) => {
        if (err) return console.error(err);
        //console.error("users found: " + usersFound);
        res.json(usersFound);
    })
});


//POST exercise form data
app.post("/api/exercise/add", (req, res) => {

    let exercise = new Exercise({
        userId: req.body.userId,
        description: req.body.description,
        duration: req.body.duration,
        date: req.body.date ? req.body.date : Date.now()
    });

    exercise.save((err, data) => {
        //console.log("created exercise: " + data);
        if (err) return console.error(err);
        User.findById(exercise.userId, (err, userFound) => {
            if (err) return console.error(err);
            //console.log("userFound " + userFound.username); 
            res.json({
                _id: data.userId,
                username: userFound.username,
                date: data.date.toDateString(),
                duration: data.duration,
                description: data.description
            });
        });
    });
});


//GET exercise log
app.get("/api/exercise/log", (req, res) => {
    console.log(req.query.userId);
    console.log(req.query.from);
    console.log(req.query.to);
    console.log(req.query.limit);

    let userId = req.query.userId;
    let limit = Number(req.query.limit);

    //create query filter
    let filter = {};
    filter.userId = userId;

    if (req.query.from && req.query.to) {
        let fromDate = new Date(req.query.from);
        let toDate = new Date(req.query.to);
        filter.date = { $gte: fromDate, $lte: toDate };
    }

    console.log("Filter " + JSON.stringify(filter));

    const queryExercises = (done) => {
        Exercise.find(filter)
            .limit(limit)
            .exec((err, exercices) => {
                if (err) return console.error(err);
                done(exercices);
            })
    };

    const paseExercises = (exercices) => {
        let logArray = [];

        for (let i = 0; i < exercices.length; i++) {
            var obj = exercices[i];
            logArray.push({
                description: obj.description,
                duration: obj.duration,
                date: obj.date.toDateString()
            });
        }
        console.log(logArray);

        User.findById(userId, (err, userFound) => {
            if (err) return console.error(err);
            let logger = {
                _id: userId,
                username: userFound.username,
                count: logArray.length,
                log: logArray
            };
            res.json(logger);
        });
    }

    //Execute Query
    queryExercises(paseExercises);

});

File Metadata Microservice

https://repl.it/@nocin/boilerplate-project-filemetadata#server.js

https://www.npmjs.com/package/multer

var express = require('express');
var cors = require('cors');
require('dotenv').config()
var multer  = require('multer')
var upload = multer({ dest: 'uploads/' });

var app = express();

app.use(cors());
app.use('/public', express.static(process.cwd() + '/public'));

app.get('/', function (req, res) {
    res.sendFile(process.cwd() + '/views/index.html');
});


const port = process.env.PORT || 3000;
app.listen(port, function () {
  console.log('Your app is listening on port ' + port)
});


//POST 
app.post('/api/fileanalyse', upload.single('upfile'), (req, res, next) => {
  res.json({ name: req.file.originalname, type: req.file.mimetype, size: req.file.size  });
})