read-excel-file
Read *.xlsx
files in a browser or Node.js. Parse to JSON with a strict schema.
Performance
There have been some complaints about this library not being able to handle huge *.xlsx
files. It's true that this library's main point have been usability and convenience, and not performance or the ability to handle huge datasets. For example, the time of parsing a 2000 rows / 20 columns file is about 3 seconds, and when parsing a 100k+ rows file, it may throw a RangeError: Maximum call stack size exceeded
. So, for handling huge datasets, use something like xlsx
package instead. This library is suitable for handling small to medium *.xlsx
files.
Install
npm install read-excel-file --save
If you're not using a bundler then use a standalone version from a CDN.
Browser
<input type="file" id="input" />
import readXlsxFile from 'read-excel-file'
const input = document.getElementById('input')
input.addEventListener('change', () => {
readXlsxFile(input.files[0]).then((rows) => {
// `rows` is an array of rows
// each row being an array of cells.
})
})
Node.js
const readXlsxFile = require('read-excel-file/node');
// File path.
readXlsxFile('/path/to/file').then((rows) => {
// `rows` is an array of rows
// each row being an array of cells.
})
// Readable Stream.
readXlsxFile(fs.createReadStream('/path/to/file')).then((rows) => {
...
})
Dates
XLSX format has no dedicated "date" type so dates are stored internally as simply numbers along with a "format" (e.g. "MM/DD/YY"
). When using readXlsx()
with schema
parameter all dates get parsed correctly in any case. But if using readXlsx()
without schema
parameter (to get "raw" data) then this library attempts to guess whether a cell value is a date or not by examining the cell "format" (e.g. "MM/DD/YY"
), so in most cases dates are detected and parsed automatically. For exotic cases one can pass an explicit dateFormat
parameter (e.g. "MM/DD/YY"
) to instruct the library to parse numbers with such "format" as dates.
JSON
To convert rows to JSON pass schema
option to readXlsxFile()
. It will return { rows, errors }
object instead of just rows
.
// An example *.xlsx document:
// -----------------------------------------------------------------------------------------
// | START DATE | NUMBER OF STUDENTS | IS FREE | COURSE TITLE | CONTACT | STATUS |
// -----------------------------------------------------------------------------------------
// | 03/24/2018 | 123 | true | Chemistry | (123) 456-7890 | SCHEDULED |
// -----------------------------------------------------------------------------------------
const schema = {
'START DATE': {
prop: 'date',
type: Date
// Excel stores dates as integers.
// E.g. '24/03/2018' === 43183.
// Such dates are parsed to UTC+0 timezone with time 12:00 .
},
'NUMBER OF STUDENTS': {
prop: 'numberOfStudents',
type: Number,
required: true
},
// 'COURSE' is not a real Excel file column name,
// it can be any string — it's just for code readability.
'COURSE': {
prop: 'course',
type: {
'IS FREE': {
prop: 'isFree',
type: Boolean
// Excel stored booleans as numbers:
// `1` is `true` and `0` is `false`.
// Such numbers are parsed to booleans.
},
'COURSE TITLE': {
prop: 'title',
type: String
}
}
},
'CONTACT': {
prop: 'contact',
required: true,
parse(value) {
const number = parsePhoneNumber(value)
if (!number) {
throw new Error('invalid')
}
return number
}
},
'STATUS': {
prop: 'status',
type: String,
oneOf: [
'SCHEDULED',
'STARTED',
'FINISHED'
]
}
}
readXlsxFile(file, { schema }).then(({ rows, errors }) => {
// `errors` have shape `{ row, column, error, value }`.
errors.length === 0
rows === [{
date: new Date(2018, 2, 24),
numberOfStudents: 123,
course: {
isFree: true,
title: 'Chemistry'
},
contact: '+11234567890',
}]
})
There are also some additional exported type
s:
-
"Integer"
for parsing integerNumber
s. -
"URL"
for parsing URLs. -
"Email"
for parsing email addresses.
A schema entry for a column can also have a validate(value)
function for validating the parsed value. It must throw
an Error
if the value is invalid.
A React component for displaying error info could look like this:
import { parseExcelDate } from 'read-excel-file'
function ParseExcelError({ children: error }) {
// Human-readable value.
let value = error.value
if (error.type === Date) {
value = parseExcelDate(value).toString()
}
// Error summary.
return (
<div>
<code>"{error.error}"</code>
{' for value '}
<code>"{value}"</code>
{' in column '}
<code>"{error.column}"</code>
{error.type && ' of type '}
{error.type && <code>"{error.type.name}"</code>}
{' in row '}
<code>"{error.row}"</code>
</div>
)
}
When using a schema
there's also an optional transformData(data)
parameter which can be used for the cases when the spreadsheet rows/columns aren't in the correct format. For example, the heading row may be missing, or there may be some purely presentational or empty rows. Example:
readXlsxFile(file, {
schema,
transformData(data) {
// Adds header row to the data.
return ['ID', 'NAME', ...].concat(data)
// Removes empty rows.
return data.filter(row => row.filter(column => column !== null).length > 0)
}
})
Browser compatibility
Node.js *.xlxs
parser uses xpath
and xmldom
packages for XML parsing. The same packages could be used in a browser because all modern browsers (except IE 11) have native DOMParser
built-in which could is used instead (meaning smaller footprint and better performance) but since Internet Explorer 11 support is still required the browser version doesn't use the native DOMParser
and instead uses xpath
and xmldom
packages for XML parsing just like the Node.js version.
Gotchas
Formulas
Dynamically calculated cells using formulas (SUM
, etc) are not supported.
Advanced
By default it reads the first sheet in the document. If you have multiple sheets in your spreadsheet then pass either sheet: number
(sheet index, starting from 1
) or sheet: string
(sheet name) as part of the options
argument (options.sheet
is 1
by default):
readXlsxFile(file, { sheet: 2 }).then((data) => {
...
})
readXlsxFile(file, { sheet: 'Sheet1' }).then((data) => {
...
})
To get the list of sheets one can pass getSheets: true
option:
readXlsxFile(file, { getSheets: true }).then((sheets) => {
// sheets === [{ name: 'Sheet1' }, { name: 'Sheet2' }]
})
CDN
One can use any npm CDN service, e.g. unpkg.com or jsdelivr.net
<script src="https://unpkg.com/read-excel-file@4.x/bundle/read-excel-file.min.js"></script>
<script>
var input = document.getElementById('input')
input.addEventListener('change', function() {
readXlsxFile(input.files[0]).then(function() {
// `rows` is an array of rows
// each row being an array of cells.
})
})
</script>
References
For XML parsing xmldom
and xpath
are used.