Develop Reference

How to Read data from Excel sheet using javascript [duplicate]

I am able to read Excel file via FileReader but it outputs text as well as weird characters with it. I need to read xls file row-wise, read data in every column and convert it to JSON.
How to read xls file row by row?

Below Function converts the Excel sheet (XLSX format) data to JSON. you can add promise to the function.
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/jszip.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/xlsx.js"></script>
<script>
var ExcelToJSON = function() {
this.parseExcel = function(file) {
var reader = new FileReader();
reader.onload = function(e) {
var data = e.target.result;
var workbook = XLSX.read(data, {
type: 'binary'
});
workbook.SheetNames.forEach(function(sheetName) {
// Here is your object
var XL_row_object = XLSX.utils.sheet_to_row_object_array(workbook.Sheets[sheetName]);
var json_object = JSON.stringify(XL_row_object);
console.log(json_object);
})
};
reader.onerror = function(ex) {
console.log(ex);
};
reader.readAsBinaryString(file);
};
};
</script>
Below post has the code for XLS format Excel to JSON javascript code?

Old question, but I should note that the general task of parsing XLS files from javascript is tedious and difficult but not impossible.
I have basic parsers implemented in pure JS:
http://oss.sheetjs.com/js-xls/ (XLS files, what you wanted)
http://oss.sheetjs.com/js-xlsx/ (XLSX/XLSM/XLSB files)
Both pages are HTML5 File API-driven XLS/XLSX parsers (you can drag-drop your file and it will print out the data in the cells in a comma-separated list). You can also generate JSON objects (assuming the first row is a header row).
The test suite http://oss.sheetjs.com/ shows a version that uses XHR to get and parse files.

Upload an excel file here and you can get the data in JSON format in console:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/jszip.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/xlsx.js"></script>
<script>
var ExcelToJSON = function() {
this.parseExcel = function(file) {
var reader = new FileReader();
reader.onload = function(e) {
var data = e.target.result;
var workbook = XLSX.read(data, {
type: 'binary'
});
workbook.SheetNames.forEach(function(sheetName) {
// Here is your object
var XL_row_object = XLSX.utils.sheet_to_row_object_array(workbook.Sheets[sheetName]);
var json_object = JSON.stringify(XL_row_object);
console.log(JSON.parse(json_object));
jQuery('#xlx_json').val(json_object);
})
};
reader.onerror = function(ex) {
console.log(ex);
};
reader.readAsBinaryString(file);
};
};
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
var xl2json = new ExcelToJSON();
xl2json.parseExcel(files[0]);
}
</script>
<form enctype="multipart/form-data">
<input id="upload" type=file name="files[]">
</form>
<textarea class="form-control" rows=35 cols=120 id="xlx_json"></textarea>
<script>
document.getElementById('upload').addEventListener('change', handleFileSelect, false);
</script>
This is a combination of the following Stackoverflow posts:
https://stackoverflow.com/a/37083658/4742733
https://stackoverflow.com/a/39515846/4742733
Good Luck...

This code can help youMost of the time jszip.js is not working so include xlsx.full.min.js in your js code.
Html Code
<input type="file" id="file" ng-model="csvFile"
onchange="angular.element(this).scope().ExcelExport(event)"/>
Javascript
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/xlsx.js">
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/jszip.js">
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.10.8/xlsx.full.min.js">
</script>
$scope.ExcelExport= function (event) {
var input = event.target;
var reader = new FileReader();
reader.onload = function(){
var fileData = reader.result;
var wb = XLSX.read(fileData, {type : 'binary'});
wb.SheetNames.forEach(function(sheetName){
var rowObj =XLSX.utils.sheet_to_row_object_array(wb.Sheets[sheetName]);
var jsonObj = JSON.stringify(rowObj);
console.log(jsonObj)
})
};
reader.readAsBinaryString(input.files[0]);
};

If you want the simplest and tiniest way of reading an *.xlsx file in a browser then this library might do:
https://catamphetamine.gitlab.io/read-excel-file/
<input type="file" id="input" />
import readXlsxFile from 'read-excel-file'
const input = document.getElementById('input')
input.addEventListener('change', () => {
readXlsxFile(input.files[0]).then((data) => {
// `data` is an array of rows
// each row being an array of cells.
})
})
In the example above data is raw string data.
It can be parsed to JSON with a strict schema by passing schema argument. See API docs for an example of that.
API docs:
http://npmjs.com/package/read-excel-file

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/jszip.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.8.0/xlsx.js"></script>
<script>
var ExcelToJSON = function() {
this.parseExcel = function(file) {
var reader = new FileReader();
reader.onload = function(e) {
var data = e.target.result;
var workbook = XLSX.read(data, {
type: 'binary'
});
workbook.SheetNames.forEach(function(sheetName) {
// Here is your object
var XL_row_object = XLSX.utils.sheet_to_row_object_array(workbook.Sheets[sheetName]);
var json_object = JSON.stringify(XL_row_object);
console.log(JSON.parse(json_object));
jQuery( '#xlx_json' ).val( json_object );
})
};
reader.onerror = function(ex) {
console.log(ex);
};
reader.readAsBinaryString(file);
};
};
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
var xl2json = new ExcelToJSON();
xl2json.parseExcel(files[0]);
}
</script>
<form enctype="multipart/form-data">
<input id="upload" type=file name="files[]">
</form>
<textarea class="form-control" rows=35 cols=120 id="xlx_json"></textarea>
<script>
document.getElementById('upload').addEventListener('change', handleFileSelect, false);
</script>

Thank you for the answer above, I think the scope (of answers) is completed but I would like to add a "react way" for whoever using react.
Create a file called importData.js:
import React, {Component} from 'react';
import XLSX from 'xlsx';
export default class ImportData extends Component{
constructor(props){
super(props);
this.state={
excelData:{}
}
}
excelToJson(reader){
var fileData = reader.result;
var wb = XLSX.read(fileData, {type : 'binary'});
var data = {};
wb.SheetNames.forEach(function(sheetName){
var rowObj =XLSX.utils.sheet_to_row_object_array(wb.Sheets[sheetName]);
var rowString = JSON.stringify(rowObj);
data[sheetName] = rowString;
});
this.setState({excelData: data});
}
loadFileXLSX(event){
var input = event.target;
var reader = new FileReader();
reader.onload = this.excelToJson.bind(this,reader);
reader.readAsBinaryString(input.files[0]);
}
render(){
return (
<input type="file" onChange={this.loadFileXLSX.bind(this)}/>
);
}
}
Then you can use the component in the render method like:
import ImportData from './importData.js';
import React, {Component} from 'react';
class ParentComponent extends Component{
render(){
return (<ImportData/>);
}
}
<ImportData/> would set the data to its own state, you can access Excel data in the "parent component" by following this:

readExcelFile = async ( file ) =>
{
const fileReader = new FileReader();
fileReader.readAsArrayBuffer( file );
fileReader.onload = ( e ) =>
{
const bufferArray = e.target.result;
const wb = XLSX.read( bufferArray, { type: "buffer" } );
const wsname = wb.SheetNames[ 0 ];
const ws = wb.Sheets[ wsname ];
const data = XLSX.utils.sheet_to_json( ws );
console.log(data);
};
};
<input type="file" name="excelfile" id="excelfile" readExcelFile(file)>

Simplest way to do it using CDN with plain javascript
<script src="https://unpkg.com/read-excel-file#5.x/bundle/read-excel-file.min.js"></script>
<html>
<h1>read-excel-file</h1>
</html>
<script>
var input = document.createElement("INPUT");
input.setAttribute("type", "file");
document.body.appendChild(input)
input.addEventListener('change', function() {
readXlsxFile(input.files[0]).then(function(rows) {
console.log(rows)
})
})
</script>
Simplest way to it using plain javascript.

If you are ever wondering how to read a file from server this code might be helpful.
Restrictions :
File should be in the server (Local/Remote).
You will have to setup headers or have CORS google plugin.
<Head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script lang="javascript" src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.12.4/xlsx.core.min.js"></script>
</head>
<body>
<script>
/* set up XMLHttpRequest */
// replace it with your file path in local server
var url = "http://localhost/test.xlsx";
var oReq = new XMLHttpRequest();
oReq.open("GET", url, true);
oReq.responseType = "arraybuffer";
oReq.onload = function(e) {
var arraybuffer = oReq.response;
/* convert data to binary string */
var data = new Uint8Array(arraybuffer);
var arr = new Array();
for (var i = 0; i != data.length; ++i) {
arr[i] = String.fromCharCode(data[i]);
}
var bstr = arr.join("");
var cfb = XLSX.read(bstr, { type: 'binary' });
cfb.SheetNames.forEach(function(sheetName, index) {
// Obtain The Current Row As CSV
var fieldsObjs = XLS.utils.sheet_to_json(cfb.Sheets[sheetName]);
fieldsObjs.map(function(field) {
$("#my_file_output").append('<input type="checkbox" value="' + field.Fields + '">' + field.Fields + '<br>');
});
});
}
oReq.send();
</script>
</body>
<div id="my_file_output">
</div>
</html>

include the xslx.js , xlsx.full.min.js , jszip.js
add a onchange event handler to the file input
function showDataExcel(event)
{
var file = event.target.files[0];
var reader = new FileReader();
var excelData = [];
reader.onload = function (event) {
var data = event.target.result;
var workbook = XLSX.read(data, {
type: 'binary'
});
workbook.SheetNames.forEach(function (sheetName) {
// Here is your object
var XL_row_object = XLSX.utils.sheet_to_row_object_array(workbook.Sheets[sheetName]);
for (var i = 0; i < XL_row_object.length; i++)
{
excelData.push(XL_row_object[i]["your column name"]);
}
var json_object = JSON.stringify(XL_row_object);
console.log(json_object);
alert(excelData);
})
};
reader.onerror = function (ex) {
console.log(ex);
};
reader.readAsBinaryString(file);
}

This is for react js
import React, { useState } from "react";
import logo from "./logo.svg";
import "./App.css";
import * as XLSX from "xlsx";
function App() {
const [items, setItems] = useState([]);
const readExcel = (file) => {
const promise = new Promise((resolve, reject) => {
const fileReader = new FileReader();
fileReader.readAsArrayBuffer(file);
fileReader.onload = (e) => {
const bufferArray = e.target.result;
const wb = XLSX.read(bufferArray, { type: "buffer" });
const wsname = wb.SheetNames[0];
const ws = wb.Sheets[wsname];
const data = XLSX.utils.sheet_to_json(ws);
resolve(data);
};
fileReader.onerror = (error) => {
reject(error);
};
});
promise.then((d) => {
setItems(d);
});
};
return (
<div>
<input
type="file"
onChange={(e) => {
const file = e.target.files[0];
readExcel(file);
}}
/>
<table class="table container">
<thead>
<tr>
<th scope="col">Item</th>
<th scope="col">Description</th>
</tr>
</thead>
<tbody>
{items.map((d) => (
<tr key={d.Item}>
<th>{d.Item}</th>
<td>{d.Description}</td>
</tr>
))}
</tbody>
</table>
</div>
);
}
export default App;

Below code will work in reading XLSX file using Javascript
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.7.7/xlsx.core.min.js"></script>
<script>
function handleFile(e)
{
//Get the files from Upload control
var files = e.target.files;
var i, f;
var title;
var choice;
//Loop through files
for (i = 0, f = files[i]; i != files.length; ++i)
{
var reader = new FileReader();
var name = f.name;
reader.onload = function(e)
{
debugger;
var data = e.target.result;
var result;
var workbook = XLSX.read(data,
{
type: 'binary'
});
var sheet_name_list = workbook.SheetNames;
var roa;
sheet_name_list.forEach(function(y)
{
/* iterate through sheets */
//Convert the cell value to Json
roa = XLSX.utils.sheet_to_json(workbook.Sheets[y]);
if (roa.length > 0)
{
result = roa;
}
});
};
reader.readAsArrayBuffer(f);
}
}
$(document).ready(function()
{
$('#files').change(handleFile);
});
</script>
<input type="file" id="files" name="files"/>

The weird characters you got from reading the Excel file from the FileReader API comes from the structure of the file that differs a lot from a text file.
So reading it as text with the FileReader API will give those weirds character as a result.
What you can do is to use the FileReader API to read it as a binary string.
At this point if you try to log that binary string you will also get weirds characters.
In order to get your file content you need to parse that binary string to extract the data it contains. This can be done quite easily using SheetJS.
import { read, writeFileXLSX, utils } from "https://cdn.sheetjs.com/xlsx-0.18.7/package/xlsx.mjs";
const workbook = read(data, {
type:'binary',
});
data is the binary string resulting from reading an Excel file as a binary string with the FileReader API.
workbook is an object that contains all the data of your file.
The workbook.Sheets instruction will give you access to all the sheets that are in the file.
workbook.Sheets.sheet1 will give you access to the content of the first sheet of the file.
All the related arrays are from the {key:value} type.
The content of a sheet accessed this way is a single dimension object array wich contains all the cells of the sheet starting from the first cell of the header to the last cell wich contains data. Each of those cells has a key like this 'A1', 'B250', 'J3'
This array also have two more entries with those keys '!margin' and '!ref':
'!margin' refers to cells margins so it may not represent any interest.
'!ref' is more interesting as it contains the plage of cells containing data wich is a string like this 'A1:J215' from it you could get the amount of lines or the char of the last column.
If you want more informations you could check the SheetJS documentation and there is a more detailed example here : How to read an excel file contents on client side?
Note :
If you want to use this import statement in an html page you'll need to do it inside those scripts tags : <script type="module" defer> ... </script>
Here is a codepen where you can test this method. There's only the most basic method. There are some shorter ways to do the same by using the SheetJS utils functions to convert directly the sheet content to another format.

XLS is a binary proprietary format used by Microsoft. Parsing XLS with server side languages is very difficult without using some specific library or Office Interop. Doing this with javascript is mission impossible. Thanks to the HTML5 File API you can read its binary contents but in order to parse and interpret it you will need to dive into the specifications of the XLS format. Starting from Office 2007, Microsoft embraced the Open XML file formats (xslx for Excel) which is a standard.

var excel=new ActiveXObject("Excel.Application");
var book=excel.Workbooks.Open(your_full_file_name_here.xls);
var sheet=book.Sheets.Item(1);
var value=sheet.Range("A1");
when you have the sheet. You could use VBA functions as you do in Excel.

Read a csv or excel (xlsx) file with just javascript and html?

Is it possible to read a excel xlsx or csv, preferably xlsx, using just JavaScript and html. All the solutions (sheetsJS, d3{d3 uses the Fetch API}) I have found require a webserver. I understand I can get a simple webserver using web server for chrome or python or node.js. Futhermore, I understand I can run chrome with certain flags, but I would like to not do this because of security concerns. I am building a demo for someone who is not web savvy and would like to avoid doing this.
my file structure is very simple :
TestFolder
| index.html
| js/
| test.js
| data/
| test.xlsx
| css/
| test.css
I simply need to read the xlsx and then display that data in html page.

I've added a simple example that accepts Excel or CSV files (current example accepts a single file), uses the SheetJS library to parse the Excel file type, convert the data to JSON and logs the contents to the console.
This should be more than enough to complete your demo. Hope this helps!
var file = document.getElementById('docpicker')
var viewer = document.getElementById('dataviewer')
file.addEventListener('change', importFile);
function importFile(evt) {
var f = evt.target.files[0];
if (f) {
var r = new FileReader();
r.onload = e => {
var contents = processExcel(e.target.result);
console.log(contents)
}
r.readAsBinaryString(f);
} else {
console.log("Failed to load file");
}
}
function processExcel(data) {
var workbook = XLSX.read(data, {
type: 'binary'
});
var firstSheet = workbook.SheetNames[0];
var data = to_json(workbook);
return data
};
function to_json(workbook) {
var result = {};
workbook.SheetNames.forEach(function(sheetName) {
var roa = XLSX.utils.sheet_to_json(workbook.Sheets[sheetName], {
header: 1
});
if (roa.length) result[sheetName] = roa;
});
return JSON.stringify(result, 2, 2);
};
<script src="https://cdnjs.cloudflare.com/ajax/libs/xlsx/0.14.3/xlsx.full.min.js"></script>
<label for="avatar">Choose an Excel or CSV file:</label>
<input type="file" id="docpicker" accept=".csv,application/vnd.ms-excel,.xlt,application/vnd.ms-excel,.xla,application/vnd.ms-excel,.xlsx,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,.xltx,application/vnd.openxmlformats-officedocument.spreadsheetml.template,.xlsm,application/vnd.ms-excel.sheet.macroEnabled.12,.xltm,application/vnd.ms-excel.template.macroEnabled.12,.xlam,application/vnd.ms-excel.addin.macroEnabled.12,.xlsb,application/vnd.ms-excel.sheet.binary.macroEnabled.12">
<div id="dataviewer">

You could try using the Fetch API to download the file and process it with JavaScript.
fetch('data/test.xlsx').then(function(resp) {
// Process the data here...
console.log('Data Response: ', resp);
});
It would be much easier to work with if your data file was in JSON format, but this might work for your needs.
Update - Example when the data is in JSON format
fetch('data/test.xlsx').then(function(resp) {
var records = resp.json(); // Assuming that we receive a JSON array.
console.log('Records: ', records.length);
records.forEach(function(record){
console.log('Record Name: ', record.name); // Assuming each record has a name property
});
});

Here is how I ended up doing it:
I got error w/ readAsBinaryString so I went out w/ the below. I noted that sheet_to_json didn't work w/ csv so I ran that first and checked results and parsed sheet_to_csv if sheet_to_json === 0.
HTML:
<!-- SheetsJS CSV & XLSX -->
<script src="xlsx/xlsx.full.min.js"></script>
<!-- SheetsJS CSV & XLSX -->
<!-- CSV/XLSX -->
<div class="ms-font-xl ms-settings__content__subtitle">CSV/XLSX Upload:</div>
<input type="file" id="csv-xlsx-file" accept=".csv,application/vnd.ms-excel,.xlt,application/vnd.ms-excel,.xla,application/vnd.ms-excel,.xlsx,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet,.xltx,application/vnd.openxmlformats-officedocument.spreadsheetml.template,.xlsm,application/vnd.ms-excel.sheet.macroEnabled.12,.xltm,application/vnd.ms-excel.template.macroEnabled.12,.xlam,application/vnd.ms-excel.addin.macroEnabled.12,.xlsb,application/vnd.ms-excel.sheet.binary.macroEnabled.12">
<!-- CSV/XLSX -->
JS:
var csv_file_elm = document.getElementById("csv-xlsx-file")
csv_file_elm.addEventListener('change', CSV_XLSX_File_Selected_Event)
async function CSV_XLSX_File_Selected_Event() {
var id = this.id
var inputElement = document.getElementById(id)
let ext = inputElement.value
ext = ext.split(".")
ext = ext[ext.length - 1]
var files = inputElement.files || [];
if (!files.length) return;
var file = files[0];
var reader = new FileReader();
reader.onloadend = async function (event) {
var arrayBuffer = reader.result;
var options = { type: 'array' };
var workbook = XLSX.read(arrayBuffer, options);
//console.timeEnd();
var sheetName = workbook.SheetNames
var sheet = workbook.Sheets[sheetName]
var sheet_to_html = XLSX.utils.sheet_to_html(sheet)
var sheet_to_json = XLSX.utils.sheet_to_json(sheet)
if (sheet_to_json.length === 0) {
var sheet_to_csv = [XLSX.utils.sheet_to_csv(sheet)]
var results = sheet_to_csv
}
if (sheet_to_json.length > 0) {
var results = sheet_to_json
}
let Parsed_File_Obj = {
"sheet_to_html": sheet_to_html,
"results": results,
"ext": ext,
}
console.log('Parsed_File_Obj')
console.log(Parsed_File_Obj)
};
reader.readAsArrayBuffer(file);
}

Import Data From Excel To MySql With Node JS

I want to read excel to save in MySQL database by using NodeJS. I do not know what library to use. I want to be able to read excel based on certain rows and columns. Please help me.

There are many libraries that you can use :
sheetjs/xlsx
excel.js
etc.

There's a great library SheetJS/js-xlsx that provides an API for reading Excel documents.
For example, if you are uploading a file, you'll end up with something like this:
var XLSX = require('xlsx');
function importFromExcel(file) {
var reader = new FileReader();
reader.onload = function (e) {
/* read workbook */
var bstr = e.target.result;
var workbook = XLSX.read(bstr, { type: 'binary' });
/* for each sheet, grab a sheet name */
workbook.SheetNames.forEach(function (workSheetName, index) {
var sheetName = workbook.SheetNames[index];
var workSheet = workbook.Sheets[sheetName];
var excelData = (XLSX.utils.sheet_to_json(workSheet, { header: 1 }));
mapExcelData(excelData); // do whatever you want with your excel data
});
};
reader.readAsBinaryString(file);
}
function mapExcelData(data) {...}

Convert binary file to JavaScript string and then to Uint8Array

I'm trying to create a web application that can be used via a file:// URI. This means that I can't use AJAX to load binary files (without turning off security features in the browser, which I don't want to do as a matter of principle).
The application uses a SQLite database. I want to provide the database to a sql.js constructor, which requires it in Uint8Array format.
Since I can't use AJAX to load the database file, I could instead load it with <input type="file"> and FileReader.prototype.readAsArrayBuffer and convert the ArrayBuffer to a Uint8Array. And that's working with the following code:
input.addEventListener('change', function (changeEvent) {
var file = changeEvent.currentTarget.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (loadEvent) {
var buffer = loadEvent.target.result;
var uint8Array = new Uint8Array(buffer);
var db = new sql.Database(uint8Array);
});
reader.readAsArrayBuffer(file);
});
However, <input type="file"> requires user interaction, which is tedious.
I thought I might be able to work around the no-AJAX limitation by using a build tool to convert my database file to a JavaScript object / string and generate a ".js" file providing the file contents, and then convert the file contents to a Uint8Array, somehow.
Psuedocode:
// In Node.js:
var fs = require('fs');
var sqliteDb = fs.readFileSync('path/to/sqlite.db');
var string = convertBufferToJsStringSomehow(sqliteDb);
fs.writeFileSync('build/db.js', 'var dbString = "' + string + '";');
// In the browser (assume "build/db.js" has been loaded via a <script> tag):
var uint8Array = convertStringToUint8ArraySomehow(dbString);
var db = new sql.Database(uint8Array);
In Node.js, I've tried the following:
var TextEncoder = require('text-encoding').TextEncoder;
var TextDecoder = require('text-encoding').TextEncoder;
var sql = require('sql.js');
var string = new TextDecoder('utf-8').decode(fs.readFileSync('path/to/sqlite.db'));
// At this point, I would write `string` to a ".js" file, but for
// the sake of determining if converting back to a Uint8Array
// would work, I'll continue in Node.js...
var uint8array = new TextEncoder().encode(string);
var db = new sql.Database(uint8array);
db.exec('SELECT * FROM tablename');
But when I do that, I get the error "Error: database disk image is malformed".
What am I doing wrong? Is this even possible? The database disk image isn't "malformed" when I load the same file via FileReader.

Using the following code, I was able to transfer the database file's contents to the browser:
// In Node.js:
var fs = require('fs');
var base64 = fs.readFileSync('path/to/sqlite.db', 'base64');
fs.writeFileSync('build/db.js', 'var dbString = "' + base64 + '";');
// In the browser (assume "build/db.js" has been loaded via a <script> tag):
function base64ToUint8Array (string) {
var raw = atob(string);
var rawLength = raw.length;
var array = new Uint8Array(new ArrayBuffer(rawLength));
for (var i = 0; i < rawLength; i += 1) {
array[i] = raw.charCodeAt(i);
}
return array;
}
var db = new sql.Database(base64ToUint8Array(dbString));
console.log(db.exec('SELECT * FROM tablename'));

And that's working with the following code:
input.addEventListener('change', function (changeEvent) {
var file = changeEvent.currentTarget.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (loadEvent) {
var buffer = loadEvent.target.result;
var uint8Array = new Uint8Array(buffer);
var db = new sql.Database(uint8Array);
});
reader.readAsArrayBuffer(file);
});
However, <input type="file"> requires user interaction, which is
tedious.
Using current working approach would be less tedious than attempting to create workarounds. If user intends to use application, user can select file from their filesystem to run application.

HTML5 FileReader + WebSQL

Ist it possible to parse a csv-file with FileReader an write it a WebSql Table?

The FileReader.readAsText() method will give you a string from the file which you can then split() to get the lines and csv cells. Check out readAsText() for more details and try pasting the following in to the interactive example:
<script id='csv' type='text/plain'>
apple,1,$1.00
banana,4,$0.20
orange,3,$0.79
</script>
<script>
// Use a Blob to simulate a File
var csv = document.getElementById('csv').textContent.trim();
var file = new Blob([csv]);
var reader = new FileReader();
reader.onload = function(event){
var reader = event.target;
var text = reader.result;
var lines = text.split('\n');
lines.forEach(function(line) {
var parts = line.split(',');
// process the cells in the csv
console.log(parts[0], parts[1], parts[2]);
});
};
reader.readAsText(file);
</script>

Yes, that should not be a problem at all :)
Just use FileReader.readAsText() to grab the csv file content, and from there it should be a breeze

With Screw-FileReader
// Use a Blob to simulate a File
let blob = new Blob([
`apple,1,$1.00
banana,4,$0.20
orange,3,$0.79`
])
blob.text().then(text => {
var lines = text.split('\n')
for (let line of lines) {
let parts = line.split(',')
// process the cells in the csv
console.log(parts)
}
})
<script src="https://cdn.rawgit.com/jimmywarting/Screw-FileReader/master/index.js"></script>