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SheetJS is a JavaScript library for reading and writing data from spreadsheets.
JavaScript code cannot be directly executed on most modern computers. A software component ("JavaScript engine") executes code. After embedding a JS engine, programs can leverage SheetJS libraries to process spreadsheets and data.
The demos in this section showcase a number of JS engines and language bindings. In each case, we will build a sample application that embeds a JS engine, loads SheetJS library scripts, and reads and writes spreadsheet files.
General Caveats
There are many JS engines with different design goals. Some are designed for low-power or low-memory environments. Others aim for interoperability with specific programming languages or environments. Typically they support ES3 and are capable of running SheetJS code.
Common browser and NodeJS APIs are often missing from light-weight JS engines.
Global
Some engines do not provide globalThis or global or window. A global
variable can be exposed in one line that should be run in the JS engine:
var global = (function(){ return this; }).call(null);
Console
Some engines do not provide a console object but offer other ways to print to
standard output. For example, Hermes1 provides print(). A console object
should be created using the engine print function:
var console = { log: function(x) { print(x); } };
Binary Data
Some engines do not provide easy ways to exchange binary data. For example, some libraries pass null-terminated arrays, which would truncate XLSX, XLS, and other exports. APIs that accept pointers without length should be avoided.
Base64 strings are safe, as they do not use null characters, but should only be
used when there is no safe way to pass ArrayBuffer or Uint8Array objects.
The SheetJS read2 and write3 methods directly support Base64 strings.
Byte Conventions
Java has no native concept of unsigned bytes. Values in a byte[] are limited
to the range -128 .. 127. They need to be fixed within the JS engine.
Some engines support typed arrays. The Uint8Array constructor will fix values:
var signed_data = [-48, -49, 17, -32, /* ... */]; // 0xD0 0xCF 0x11 0xE0 ...
var fixed_data = new Uint8Array(signed_data);
When Uint8Array is not supported, values can be fixed with bitwise operations:
var signed_data = [-48, -49, 17, -32, /* ... */]; // 0xD0 0xCF 0x11 0xE0 ...
var fixed_data = new Array(signed_data.length);
for(var i = 0; i < signed_data.length; ++i) fixed_data[i] = signed_data[i] & 0xFF;
Engines
:::info pass
Demos are tested across multiple operating systems (Windows, MacOS and Linux) across multiple architectures (x64 and ARM64).
:::
Boa
Boa is an embeddable JS engine written in Rust.
This demo has been moved to a dedicated page.
ChakraCore
ChakraCore is an embeddable JS engine written in C++.
This demo has been moved to a dedicated page.
Duktape
Duktape is an embeddable JS engine written in C. It has been ported to a number of exotic architectures and operating systems.
This demo has been moved to a dedicated page. The demo includes examples in C, Perl, PHP, Python and Zig.
Goja
Goja is a pure Go implementation of ECMAScript 5.
This demo has been moved to a dedicated page.
Hermes
Hermes is an embeddable JS engine written in C++.
This demo has been moved to a dedicated page.
JavaScriptCore
iOS and MacOS ship with the JavaScriptCore framework for running JS code from Swift and Objective-C.
This demo has been moved to a dedicated page.
JerryScript
JerryScript is a lightweight JavaScript engine designed for use in low-memory environments including microcontrollers.
This demo has been moved to a dedicated page.
Jint
Jint is an embeddable JS engine for .NET written in C#.
This demo has been moved to a dedicated page.
Nashorn
Nashorn shipped with some versions of Java. It is now a standalone library.
This demo has been moved to a dedicated page.
QuickJS
QuickJS is an embeddable JS engine written in C. It provides a separate set of functions for interacting with the filesystem and the global object. It can run the standalone browser scripts.
This demo has been moved to a dedicated page.
Rhino
Rhino is an ES3+ engine in Java.
This demo has been moved to a dedicated page.
V8
V8 is an embeddable JS engine written in C++. It powers Chromium and Chrome, NodeJS and Deno, Adobe UXP and other platforms.
This demo has been moved to a dedicated page. The demo includes examples in C++ and Rust.
The "Python + Pandas" demo uses V8 with Python.
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See "Initialize Hermes" in the Hermes demo. ↩︎