DEV Community: Shadab Majid Shaikh

Git Guide

Shadab Majid Shaikh — Fri, 14 May 2021 11:52:09 +0000

I found this GitHub repository. Once you gone through basic git commands, you can read this. This repository contains some advanced commands very useful in day-to-day tasks.

git.io/git-tips

Role-based access to API in Node.js

Shadab Majid Shaikh — Sun, 17 May 2020 17:50:25 +0000

Let's start with a simple example of a college management system.

Can students modify their marks? => NO, students are not authorized only teachers can do this :(

But how this is handled in the college management system, the answer is

Role-based authorization to API

How to authorize resources according to the user role, What is your approach?

1. Simple and easy approach

Let's declare authorized roles in every endpoint and check with the user role if the user's role is present in authorized roles. Hurray! You have access.
Ex:

route.get('/changemarks',(req, res) => {
    const authorizedRoles = ['teacher','admin']
    // Extract user role from req && Let's assume userRole is student
    const userRole = extractUserRole(req)
    // student is not present in authorizedRoles array 
    const isAuthorized = authorizedRoles.includes(userRole);
    if(!isAuthorized){
       // return with your customized error
    }
})

Advantage:

Simple and fast

Disadvantage:

Not easily configurable

2. Middleware in every route of your project.

Don't you think the above code should be separated out as an authorization handler? Let's add authorization handler in every request as middleware.

route.get('/changemarks', authorizationHandler(['Teacher','Admin'], (req, res) => {
})


const authorizationHandler =  (authorizedRoles) => {
  return function(req, res, next) {
    const userRole = extractUserRole(req)
    if ( !authorizedRoles.includes(userRole) ) res.redirect(...);
    else next();
  }   
})

Advantage:

Easy and only one middleware, no need to add the same code in every route.

Disadvantage:

Hard-coded authorized roles in middleware's parameter ex.['Teacher','Admin']

How to save JSON data in EXCEL file using Node.js

Shadab Majid Shaikh — Wed, 13 May 2020 17:06:27 +0000

In some scenarios, you have 3rd party API which returns data in JSON format and you need that data in excel file. How we can do this? Let's follow me up for the next 5 minutes.

Today we are saving our JSON data in the EXCEL file using an excel4node library in node.js.

Let's jump to the code and then I will explain code line by line.

Create index.js

Create package.json using

npm init

Install excel4node using

npm install --save excel4node

Define your data you want to be store in excel

    const data = [
      {
        "name":"Shadab Shaikh",
        "email":"shadab@gmail.com",
        "mobile":"1234567890"
      }
    ]

Import excel4node library

    const xl = require('excel4node');

Create a workbook and give some awesome name

    const wb = new xl.Workbook();
    const ws = wb.addWorksheet('Worksheet Name');

Now Let's define columnName

    const headingColumnNames = [
        "Name",
        "Email",
        "Mobile",
    ]

Before moving to next let's explore some functions in excel4node library

1. cell(rownumber,columnnumber)
requires 2 parameter
a. row number(starts from 1)
b. column number(starts from 1)
This function selects cell with given rowno and columnno

2. string(data) , number(data)
we can store data as string or number
just call the above functions and pass data in it.

Now write columnName in Excel file using functions in excel4node

    let headingColumnIndex = 1;
    headingColumnNames.forEach(heading => {
        ws.cell(1, headingColumnIndex++)
            .string(heading)
    });

Finally, Write our data in excel file

(Don't forget to start row number from 2)

    let rowIndex = 2;
    data.forEach( record => {
        let columnIndex = 1;
        Object.keys(record ).forEach(columnName =>{
            ws.cell(rowIndex,columnIndex++)
                .string(record [columnName])
        });
        rowIndex++;
    });

Now Let's take workbook and save it into the file

    wb.write('filename.xlsx');

Here is full code, just copy and paste in your favorite editor to go through demo.

const xl = require('excel4node');
const wb = new xl.Workbook();
const ws = wb.addWorksheet('Worksheet Name');

const data = [
 {
    "name":"Shadab Shaikh",
    "email":"shadab@gmail.com",
    "mobile":"1234567890"
 }
]

const headingColumnNames = [
    "Name",
    "Email",
    "Mobile",
]

//Write Column Title in Excel file
let headingColumnIndex = 1;
headingColumnNames.forEach(heading => {
    ws.cell(1, headingColumnIndex++)
        .string(heading)
});

//Write Data in Excel file
let rowIndex = 2;
data.forEach( record => {
    let columnIndex = 1;
    Object.keys(record ).forEach(columnName =>{
        ws.cell(rowIndex,columnIndex++)
            .string(record [columnName])
    });
    rowIndex++;
}); 
wb.write('TeacherData.xlsx');