ExtendScript adds some features to a limited form of ECMAScript version 3. With the included shim, the library can run within Photoshop and other Adobe apps!
The main file is test.jsx. Target-specific files prepend target directives.
Copy the test.jsx file as well as the shim.js and xlsx.core.min.js files
to wherever you want the scripts to reside.
The demo shows opening a file and converting to an array of arrays:
/* include library */
#include "shim.js"
#include "xlsx.core.min.js"
/* get data as binary string */
var filename = "sheetjs.xlsx";
var base = new File($.fileName);
var infile = File(base.path + "/" + filename);
infile.open("r");
infile.encoding = "binary";
var data = infile.read();
/* parse data */
var workbook = XLSX.read(data, {type:"binary"});
/* DO SOMETHING WITH workbook HERE */NOTE: We forked the minifier and included a patch for ExtendScript's switch statement semicolon issue.