Node js excel parser

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Read Excel Files and convert to JSON in Node.js

 var express = require('express'); 
    var app = express(); 
    var bodyParser = require('body-parser');
    var multer = require('multer');
    var xlstojson = require("xls-to-json-lc");
    var xlsxtojson = require("xlsx-to-json-lc");
    app.use(bodyParser.json());
    var storage = multer.diskStorage({ //multers disk storage settings
        destination: function (req, file, cb) {
            cb(null, './uploads/')
        },
        filename: function (req, file, cb) {
            var datetimestamp = Date.now();
            cb(null, file.fieldname + '-' + datetimestamp + '.' + file.originalname.split('.')[file.originalname.split('.').length -1])
        }
    });
    var upload = multer({ //multer settings
                    storage: storage,
                    fileFilter : function(req, file, callback) { //file filter
                        if (['xls', 'xlsx'].indexOf(file.originalname.split('.')[file.originalname.split('.').length-1]) === -1) {
                            return callback(new Error('Wrong extension type'));
                        }
                        callback(null, true);
                    }
                }).single('file');
    /** API path that will upload the files */
    app.post('/upload', function(req, res) {
        var exceltojson;
        upload(req,res,function(err){
            if(err){
                 res.json({error_code:1,err_desc:err});
                 return;
            }
            /** Multer gives us file info in req.file object */
            if(!req.file){
                res.json({error_code:1,err_desc:"No file passed"});
                return;
            }
            /** Check the extension of the incoming file and 
             *  use the appropriate module
             */
            if(req.file.originalname.split('.')[req.file.originalname.split('.').length-1] === 'xlsx'){
                exceltojson = xlsxtojson;
            } else {
                exceltojson = xlstojson;
            }
            try {
                exceltojson({
                    input: req.file.path,
                    output: null, //since we don't need output.json
                    lowerCaseHeaders:true
                }, function(err,result){
                    if(err) {
                        return res.json({error_code:1,err_desc:err, data: null});
                    } 
                    res.json({error_code:0,err_desc:null, data: result});
                });
            } catch (e){
                res.json({error_code:1,err_desc:"Corupted excel file"});
            }
        })
    }); 
    app.get('/',function(req,res){
        res.sendFile(__dirname + "/index.html");
    });
    app.listen('3000', function(){
        console.log('running on 3000...');
    });

This article shows you how to read and extract content from an Excel (.xlsx) file by using Node.js. Without any further ado, let’s get our hands dirty and start coding.

Getting Things Ready

We are going to work with a simple Excel file that contains some information as follows:

You can download the file from the link below to your computer:

https://www.kindacode.com/wp-content/uploads/2021/11/KindaCode.com-Example.xlsx.zip

Writing Code

There are many great libraries that can help us easily read Excel files, such as xlsx (SheetJS), exceljs (ExcelJS), node-xlsx (Node XLSX). In the sample project below, we will use xlsx. It’s super popular and supports TypeScript out-of-the-box.

1. Create a new folder named example (the name doesn’t matter and is totally up to you), then initialize a new Node.js project by running:

npm init

2. In your project directory, create a subfolder called src, then add an empty index.js file. Copy the Excel file you’ve downloaded before into the src folder.

Here’s the file structure:

.
├── node_modules
├── package-lock.json
├── package.json
└── src
    ├── KindaCode.com Example.xlsx
    └── index.js

3. Installing the xlsx package:

npm i xlsx

4. Below are the code snippets for index.js. There are 2 different code snippets. The first one uses the CommonJS syntax (with require), while the second one uses the ES Modules syntax (with import). Choose the one that fits your need.

CommonJS:

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

const filePath = path.resolve(__dirname, "Kindacode.com Example.xlsx");

const workbook = xlsx.readFile(filePath);
const sheetNames = workbook.SheetNames;

// Get the data of "Sheet1"
const data = xlsx.utils.sheet_to_json(workbook.Sheets[sheetNames[0]])

/// Do what you need with the received data
data.map(person => {
  console.log(`${person.Name} is ${person.Age} years old`);
})

ES Modules:

// import with ES6 Modules syntax
import path from 'path';
import xlsx from 'xlsx';

import { fileURLToPath } from 'url'
import { dirname } from 'path'
const __filename = fileURLToPath(import.meta.url)
const __dirname = dirname(__filename)

const filePath = path.resolve(__dirname, "Kindacode.com Example.xlsx");

const workbook = xlsx.readFile(filePath);
const sheetNames = workbook.SheetNames;

// Get the data of "Sheet1"
const data = xlsx.utils.sheet_to_json(workbook.Sheets[sheetNames[0]])

/// Do what you need with the received data
data.map(person => {
  console.log(`${person.Name} is ${person.Age} years old`);
})

5. Test our project:

node src/index.js

Output:

John Doe is 37 years old
Jane Doe is 37 years old
Captain is 72 years old
Voldermort is 89 years old

Conclusion

We’ve written a simple Node.js program to retrieve the data from a sheet of an Excel workbook. If you’d like to explore more new and interesting things about modern Node.js, take a look at the following articles:

• Node.js: How to Ping a Remote Server/ Website
• Best open-source ORM and ODM libraries for Node.js
• 7 Best Open-Source HTTP Request Libraries for Node.js
• Node.js: Executing a Piece of Code after a Delay
• Express + TypeScript: Extending Request and Response objects

You can also check out our Node.js category page for the latest tutorials and examples.

Node.js is an open-source and cross-platform JavaScript runtime environment that can also be used to read from a file and write to a file which can be in txt, ods, xlsx, docx, etc format.

The following example covers how an excel file(.xlsx) file is read from an excel file and then converted into JSON and also to write to it. It can be achieved using a package called xlsx to achieve our goal.

Module Installation: You can install xlsx module using the following command:

npm install xlsx

Note: For the following example, text.xlsx is a dummy data file that has been used.

Filename: test.xlsx 

Sheet 1:

Sheet 2:

So the excel file test.xlsx has 2 sheets, one having Student details and another having lecturer details.

Read Operation Filename: read.js 

Explanation: First, the npm module is included in the read.js file and then the excel file is read into a workbook i.e constant file in the above program.

The number of files in that particular excel file is available in the SheetNames property of the workbook. It can be accessed as follows:

const sheets = file.SheetNames  // Here the value of the sheets will be 2

A for loop is run until the end of the excel file starting from the first page. One of the most important functions used in the code above is the sheet_to_json() function present in the utils module of the xlsx package. It accepts a worksheet object as a parameter and returns an array of JSON objects.

There is a forEach loop which iterates through every JSON object present in the array temp and pushes it into a variable data which would contain all the data in JSON format.

Finally, the data is printed or any other modification can be performed on the array of JSON objects.

Step to run the application:

Run the read.js file using the following command:

node read.js

Output:

Write Operation In the following example, we will convert an array of JSON objects into an excel sheet and append it to the file.

Filename: write.js

Explanation: Here we have an array of JSON objects called student_data. We use two main functions in this program i.e json_to_sheet() which accepts an array of objects and converts them into a worksheet and another function is the book_append_sheet() to append the worksheet into the workbook.

Finally, all the changes are written to the test.xlsx file using writeFile() function which takes a workbook and a excel file as input parameter.

Step to run the application:

Run the read.js file using the following command:

node write.js

Output: The final test.xlsx file would look something like this: 

Sheet 1:

Sheet 2:

Sheet 3: We can see sheet 3 is appended into the test.xlsx as shown below: