Is possible VSAM access with JS? yes !

 Is possible use JS and access VSAM, really one environment IBM/zOS with VSAM , CICS , COBOL , yes, we can !

One module enables an application to read and modify VSAM datasets on z/OS.  NPM have one package, with name vsam.js  

Please, attetion : before installing, download and install IBM SDK for Node.js - z/OS.

Node.js 8.16.2 or higher is required.

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vsamObj = vsam.openSync("sample.test.vsam.ksds",
                          JSON.parse(fs.readFileSync("schema.json")));

  // Find using a string as key:
  vsamObj.find("0321", (record, err) => {
    if (record !== null) {
      assert.equal(record.key, "0321");
      record.name = "JACOB";
      record.quantity = Buffer.from([0xe5, 0xf6, 0x78, 0x9a]).toString("hex");
      vsamObj.update(record, (err) => {
        if (err !== null)
          console.log("update was successful");
        else
          console.error(err);
        vsamObj.close();
      });
    } else {
      console.error(err);
    }
  });

  // or find using binary data as key (type must be set to "hexadecimal"):
  const keybuf = Buffer.from([0xa1, 0xb2, 0xc3, 0xd4]);
  vsamObj.find(keybuf, keybuf.length, (record, err) => {
    ...

  // or find using a hexadecimal string as key (type must be set to "hexadecimal"):
  vsamObj.find("e5f6789a", (record, err) => {
    ...

  // Starting with vsam.js v3.0.0, find and update record(s) in one call synchronously:
  count = vsamObj.updateSync("f1f2f3", record);

  // or find and delete record(s) in one call:
  count = vsamObj.deleteSync("f1f2f3");

  // or find and update record(s) in one call asynchronously:
  vsamObj.update("f1f2f3", record, (count, err) => { ... });

Schema.json 

Here contains the dataset's field names and their attributes

{
  "key": {
    "type": "hexadecimal",
    "maxLength": 8
  },
  "name": {
    "type": "string",
    "maxLength": 10,
    "minLength": 1
  },
  "quantity": {
    "type": "hexadecimal",
    "maxLength": 4
  }
}