Data Processing with JE

In a production application, it is strongly recommended to use a binding for a C engine like JavaScript::Duktape

JE is a pure-Perl JavaScript engine.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses JE and SheetJS to pull data from a spreadsheet and print CSV rows. We'll explore how to load SheetJS in a JE context and process spreadsheets from Perl scripts.

The "Complete Example" section includes a complete script for reading data from XLS files, printing CSV rows, and writing FODS workbooks.

Integration Details

The SheetJS ExtendScript build can be parsed and evaluated in a JE context.

The engine deviates from ES3. Modifying prototypes can fix some behavior:

Required shim to support JE (click to show)

The following features are implemented:

• simple string charCodeAt
• Number charCodeAt (to work around string split bug)
• String match (to work around a bug when there are no matches)

Required shim to support JE

/* String#charCodeAt is missing */
var string = "";
for(var i = 0; i < 256; ++i) string += String.fromCharCode(i);
String.prototype.charCodeAt = function(n) {
  var result = string.indexOf(this.charAt(n));
  if(result == -1) throw this.charAt(n);
  return result;
};

/* workaround for String split bug */
Number.prototype.charCodeAt = function(n) { return this + 48; };

/* String#match bug with empty results */
String.prototype.old_match = String.prototype.match;
String.prototype.match = function(p) {
  var result = this.old_match(p);
  return (Array.isArray(result) && result.length == 0) ? null : result;
};

When loading the ExtendScript build, the BOM must be removed:

## Load SheetJS source
my $src = read_file('xlsx.extendscript.js', { binmode => ':raw' });
$src =~ s/^\xEF\xBB\xBF//; ## remove UTF8 BOM
my $XLSX = $je->eval($src);

Reading Files

Data should be passed as Base64 strings:

use File::Slurp;
use MIME::Base64 qw( encode_base64 );

## Set up conversion method
$je->eval(<<'EOF');
function sheetjsparse(data) { try {
  return XLSX.read(String(data), {type: "base64", WTF:1});
} catch(e) { return String(e); } }
EOF

## Read file
my $raw_data = encode_base64(read_file($ARGV[0], { binmode => ':raw' }), "");

## Call method with data
$return_val = $je->method(sheetjsparse => $raw_data);

Writing Files

Due to bugs in data interchange, it is strongly recommended to use a simple format like .fods:

use File::Slurp;

## Set up conversion method
$je->eval(<<'EOF');
function sheetjswrite(wb) { try {
  return XLSX.write(wb, { WTF:1, bookType: "fods", type: "string" });
} catch(e) { return String(e); } }
EOF

## Generate file
my $fods = $je->method(sheetjswrite => $workbook);

## Write to filesystem
write_file("SheetJE.fods", $fods);

Complete Example

Tested Deployments

This demo was tested in the following deployments:

Architecture	Version	Date
darwin-x64	0.066	2024-12-17
darwin-arm	0.066	2024-05-25
linux-x64	0.066	2024-06-29
linux-arm	0.066	2024-05-25

1. Install JE and File::Slurp through CPAN:

cpan install JE File::Slurp

There were permissions errors in some test runs:

mkdir /Library/Perl/5.30/File: Permission denied at /System/Library/Perl/5.30/ExtUtils/Install.pm line 489.

The install command should be run through sudo:

sudo cpan install JE File::Slurp

2. Download the SheetJS ExtendScript build:

curl -LO https://cdn.sheetjs.com/xlsx-0.20.3/package/dist/xlsx.extendscript.js

3. Download the demo SheetJE.pl:

curl -LO https://docs.sheetjs.com/perl/SheetJE.pl

4. Download the test file and run:

curl -LO https://docs.sheetjs.com/cd.xls
perl SheetJE.pl cd.xls

After a short wait, the contents will be displayed in CSV form. The script will also generate the spreadsheet SheetJE.fods which can be opened in LibreOffice.