Version 0.20.9 - 2024 Oct 26

Addon module written and maintained by David Wicksell dlw@linux.com
Copyright © 2012-2024 Fourth Watch Software LC

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License (AGPL) as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.

Full license text: AGPL-3.0

Contact me if you are interested in using Nodem with a different license.

Nodem is an open source addon module that integrates Node.js with the YottaDB and GT.M implementations of M, providing in-process access to their database systems and some language features, as well as networked access to their core database functionality. Nodem provides access to the basic global database handling operations, as well as providing the ability to invoke M language functions and procedures. It also supports full local symbol table management and manipulation of the M environment.

All of Nodem's APIs support synchronous operation and accept arguments passed via a single JavaScript object (except for help, which takes no arguments or an argument string, and version, which takes no arguments), containing specific per-API properties, usually global or local, and subscripts or arguments. The APIs that currently support both synchronous and asynchronous operation, as well as accepting arguments passed by-position (except version, which takes no arguments, and merge, which requires passing arguments via a JavaScript object), are: version, data, get, set, kill, merge, order, previous, nextNode, previousNode, increment, lock, unlock, function, and procedure. In order to use the asynchronous versions of those APIs, you must pass a JavaScript function, taking two arguments - conventionally error and result - as the last argument to the API. When passing arguments to those APIs by-position, the first argument would be the global (prefaced by ^), local, or intrinsic special variable string (prefaced by $ and only supported in the get and set APIs), and the next set of arguments would be each subscript (or function/procedure argument), separated as a different argument. In order to specify an intrinsic special variable (in the get or set API) when passing arguments inside of a JavaScript object, use the local property, and preface the name with a $. For the set API, the last non-function argument would be treated as the data to set into the node. Asynchronous support for the rest of the API (open, close, configure, globalDirectory, and localDirectory) is coming soon.

Nodem uses the YottaDB and GT.M C Call-in interface. YottaDB has released a faster, low-level database access API, with version r1.20, called the SimpleAPI. Nodem uses YottaDB's SimpleAPI for the data, get, set, kill, order, previous, nextNode, previousNode, increment, lock, and unlock APIs, when it is available, and falls back to the Call-in interface when it is not.

YottaDB, LLC. has created extensive documentation for Nodem.

NOTE: The Nodem Developer API and User Guide Wiki is in development.

Using Nodem with YottaDB, in the Node.js REPL:

> const ydb = require('nodem').Ydb(); // Create YottaDB connection instance - use Gtm() when connecting to GT.M
undefined
> ydb.open(); // Open connection to YottaDB
{ ok: true, pid: 12345, tid: 12345 }
> ydb.version();
'Node.js Adaptor for YottaDB: Version: 0.20.9 (ABI=131) [FWS]; YottaDB Version: 2.00'
> ydb.get({global: 'v4wTest', subscripts: [0, 2, 0]}); // write ^v4wTest(0,2,0)
{
  ok: true,
  global: 'v4wTest',
  subscripts: [ 0, 2, 0 ],
  data: '2 bags of wheat',
  defined: true
}
> ydb.get('^v4wTest', 0, 2, 0); // write ^v4wTest(0,2,0)
'2 bags of wheat'
> ydb.get({global: 'v4wTest', subscripts: [0, 2, 0]}, (error, result) => {if (!error) {console.log('result:', result);}});
undefined
> result: {
  ok: true,
  global: 'v4wTest',
  subscripts: [ 0, 2, 0 ],
  data: '2 bags of wheat',
  defined: true
}

> ydb.get('^v4wTest', 0, 2, 0, (error, result) => {if (!error) {console.log('result:', result);}});
undefined
> result: 2 bags of wheat

> ydb.set('^v4wTest', 0, 2, 0, '3 bags of wheat'); // set ^v4wTest(0,2,0)="3 bags of wheat"
true
> ydb.get({global: 'v4wTest', subscripts: [0, 2, 0]});
{
  ok: true,
  global: 'v4wTest',
  subscripts: [ 0, 2, 0 ],
  data: '3 bags of wheat',
  defined: true
}
> ydb.get({global: 'v4wTest', subscripts: ['']});
{
  ok: false,
  errorCode: 150373498,
  errorMessage:
   '(SimpleAPI),%YDB-E-NULSUBSC, DB access failed because Null subscripts are not allowed for current region,%YDB-I-GVIS, Global variable: ^v4wTest("")'
}
> ydb.close(); // Close connection to YottaDB, releasing resources and restoring terminal settings
undefined

Nodem should run on every version of Node.js starting with version 0.12.0, through the current release (v23.1.0 at this time), as well as every version of IO.js. However, in the future, both Node.js and the V8 JavaScript engine at its core, could change their APIs in a non-backwards compatible way, which might break Nodem for that version.

In order to use the Nodem addon, you will need to have YottaDB (or GT.M) installed and configured correctly, including setting up your environment with the required YottaDB (or GT.M) environment variables, or setting the appropriate options in the open API. Make sure you have either $ydb_dist (only applicable for YottaDB) or $gtm_dist set to the root of the YottaDB (or GT.M) instance before you compile Nodem, whether manually, or via npm. You will also need to have Node.js installed and working.

ATTENTION: These instructions assume that the nodem repository has been installed in your home directory. The paths will likely be different if you have installed this with npm.

NOTE: If you have installed Nodem using npm, it will attempt to build nodem.node during installation. If there is a file in the nodem directory called builderror.log, and if that file contains no build errors for nodem.node, it built without issue. It also attempts to pre-compile the v4wNode.m integration routine, and there might be warnings from that, which won't affect the building of nodem.node itself. If you downloaded Nodem any other way, including cloning it from its github repository, then you'll have to build it from source. Remember to make sure that either $ydb_dist or $gtm_dist is set to the root of the YottaDB (or GT.M) instance before building Nodem. In order to build it, while in the root of the Nodem repository, run the npm run install command, e.g.

$ cd ~/nodem
$ npm run install

or

$ node-gyp rebuild 2> builderror.log

In addition you will need to set a few environment variables, or set the appropriate configuration options in the call to the open API, in order for YottaDB (or GT.M) to find the Call-in table and the v4wNode.m routine that it maps to. The Nodem package supplies a sample environment file, called environ. It has a commented out command to set $LD_LIBRARY_PATH to $ydb_dist or $gtm_dist, which you will need to uncomment if you need it. It is located in ~/nodem/resources and can be sourced into your working environment, either directly, or from your own environment scripts or profile/login script, e.g.

$ cd ~/nodem/resources
$ source environ

or

$ echo "source ~/nodem/resources/environ" >> ~/.profile

If you don't source the environ file, then you will need to put a copy of v4wNode.m into a directory that is specified in your $ydb_routines (only applicable for YottaDB) or $gtmroutines routines path, or in the routinesPath property in your call to the open API, so that YottaDB (or GT.M) can find it. It is located in the ~/nodem/src directory. Again, if you don't source the environ file, then you will also need to define the $ydb_ci (only applicable for YottaDB) or $GTMCI environment variable, or set the callinTable property in your call to the open API, and point it at the file nodem.ci, located in the ~/nodem/resources directory, e.g.

$ export ydb_ci=~/nodem/resources/nodem.ci
$ cp ~/nodem/src/v4wNode.m ~/p

or

> const callinTable = process.env.HOME + '/nodem/resources/nodem.ci';
> const routinesPath = process.env.HOME + '/nodem/src .'; // Make sure to include your routine directories
> ydb.open({callinTable: callinTable, routinesPath: routinesPath});

NOTE: As of Nodem version 0.20.7, if $ydb_ci and $GTMCI are undefined, Nodem will use the path to the nodem.ci file within the repository, without having to set the callinTable property, by default, simplifying configuration.

NOTE: As of Nodem version 0.20.7, if $ydb_routines and $gtmroutines are undefined, Nodem will use the path to the v4wNode.m file within the repository, without having to set the routinesPath property, by default, simplifying configuration when you don't need to call other M code with the function or procedure APIs.

You can clone the repository with this command..

$ git clone https://github.com/dlwicksell/nodem.git

You can also install it via npm with this command..

$ npm install nodem

If you are having an issue installing nodem, you can try this..

$ npm install nodem --ignore-scripts

You can update to the latest version with this command..

$ npm update nodem

or

$ npm install nodem@latest

The open call does not require any arguments, and will connect with the database specified in the environment variable $ydb_gbldir (only applicable for YottaDB) or $gtmgbldir. If you have more than one database and would like to connect to a different one than what is defined in your environment, you can pass an object, with a property called either globalDirectory or namespace, defined as the path to your global directory file for that database, e.g.

> ydb.open({globalDirectory: process.env.HOME + '/data/globals/db_utf8.gld'});

Nodem supports setting up a custom routines path, for resolving calls to other M functions and procedures, via the routinesPath property. Make sure that one of the directories in the routinesPath contains the v4wNode.m routine, located in the Nodem src directory, or its compiled object, v4wNode.o, otherwise Nodem will not be fully functional. This could be used to provide some security, by giving access only to certain routines, within a Nodem process, within an environment that contains routines with unfettered access to the system in its default environment configuration, e.g.

> const HOME = process.env.HOME;
> ydb.open({routinesPath: `${HOME}/code/local/r138(${HOME}/code/local)`});

Nodem supports setting the Call-in path directly in the open call, via the callinTable property. This can be handy if you are running Nodem in an environment that has other software that uses the YottaDB (or GT.M) Call-in interface, and you don't want to worry about namespace issues. Nor would you need to set the $ydb_ci/$GTMCI environment variable, in order for Nodem to be fully functional, e.g.

> ydb.open({callinTable: process.env.HOME + '/nodem/resources/nodem.ci'});

You can configure Nodem to function as a GT.CM client, allowing Nodem to connect with a remote database. In the open method, you can set an ipAddress, and/or a tcpPort property, and Nodem will set up the environment to connect with a YottaDB (or GT.M) database on a remote server that already has a GT.CM server running on that address and port. If only ipAddress or tcpPort is defined, the other one will be set with a default value; 127.0.0.1 for ipAddress, or 6789 for tcpPort. Nodem will then set the $ydb_cm_NODEM (if you are using YottaDB) or $GTCM_NODEM (if you are using GT.M) environment variable, for that Nodem process only, with the address and port you set in the open call, e.g.

> ydb.open({ipAddress: '127.0.0.1', tcpPort: 6789});

If you are using IPv6, you need to surround your IP address with square brackets, e.g.

> ydb.open({ipAddress: '[::1]', tcpPort: 6789});

You will also need to create, or modify, a global directory file that maps one or more database segments to a data file on the remote server you want to connect with, noting that the prefix to the -file= argument in the example below must be NODEM, in order to match the $ydb_cm_NODEM/$GTCM_NODEM environment variable name that Nodem sets up for you, e.g.

$ $ydb_dist/mumps -run GDE
GDE> change -segment DEFAULT -file=NODEM:/home/user/data/globals/gtcm-server.dat

Then on the server you are connecting to, make sure you have the data file set up at the same path that you set the -file= option to in the global directory of your GT.CM client configuration, and have started the GT.CM server on the same IP address and port that you configured in the open call in Nodem, e.g.

$ $ydb_dist/gtcm_gnp_server -log=gtcm.log -service=6789

NOTE: GT.CM only allows remote connections for the database access APIs, not the function nor procedure APIs. So while using Nodem in a remote GT.CM configuration, any calls to the function or procedure APIs will result in local calls, not remote [RPC] calls. Data nodes accessed by GT.CM cannot participate in transactions.

Nodem supports two different character encodings, UTF-8 and M. It defaults to UTF-8 mode. M mode is similar to ASCII, except that it utilizes all 8 bits in a byte, and it collates slightly differently. Instead of collation based only on the character codes themselves, it sorts numbers before everything else (except for the empty string). The character encoding you set in Nodem is decoupled from the underlying character encoding you have set up for the YottaDB (or GT.M) environment it is running in. So it is possible to work with UTF-8 encoded data in the database, while in Nodem, even if you haven't set up YottaDB (or GT.M) to work with UTF-8 directly. You can set it to UTF-8 mode directly by passing utf-8 or utf8, case insensitively, to the charset property. If you'd rather work with an older byte-encoding scheme, that stores all characters in a single byte, you can set charset to either m, ascii, or binary, case insensitively. One thing to keep in mind when you do so, is that Node.js internally stores data in UTF-16, but interprets data in UTF-8 in most cases. You can control this through the process stream encoding methods inside of your Node.js code. Call those methods to change the encoding to binary or ascii, and it will interpret your data as a byte encoding, using the character glyphs in your current locale, e.g.

> process.stdin.setEncoding('binary');
> process.stdout.setDefaultEncoding('binary');
> ydb.open({charset: 'm'}); // For all threads

or

> process.stdin.setEncoding('binary');
> process.stdout.setDefaultEncoding('binary');
> ydb.configure({charset: 'm'}); // For the current thread

There are currently two different data modes that Nodem supports. The mode can be set to canonical or string. The default is canonical, and interprets data using the M canonical representation. I.e. Numbers will be represented numerically, rather than as strings, and numbers collate before strings (except for the empty string). The other mode, string, interprets all data as strings, though they still collate the same as canonical mode, e.g.

> ydb.open({mode: 'canonical'}); // For all threads
> ydb.get('v4wTest', 'numOfBeds');
25

or

> ydb.configure({mode: 'string'}); // For the current thread
> ydb.get('v4wTest', 'numOfBeds');
'25'

Nodem also has a debug tracing mode, in case something doesn't seem to be working right, or you want to see what happens to data as it moves through the Nodem APIs. It has four levels of debugging, defaulting to off. The other debug levels are low, medium, and high. You can also use the numbers 0-3. The higher the debug level, the more verbose the debug output will be, e.g.

> ydb.open({debug: 'low'}); // For all threads

or

> ydb.open({debug: 2}); // For all threads

or

> ydb.configure({debug: 'high'}); // For the current thread

Nodem handles several common signals that are typically used to stop processes, by closing the database connection, resetting the controlling terminal configuration, and stopping the Node.js process. These signals include SIGINT, SIGTERM, and SIGQUIT. The handling of the SIGQUIT signal will also generate a core dump of the process. All three signal handlers are on by default. However, you can turn the signal handling on or off directly, via passing true or false to a signalHandler object (with properties for each of the signals) for each individual signal, or all of them at once, e.g.

> ydb.open({signalHandler: {sigint: true, sigterm: false, sigquit: false}});

or

> ydb.open({signalHandler: false});

Nodem supports a feature called auto-relink, which will automatically relink a routine object containing any function or procedure called by the function or procedure API. By default auto-relink is off. You can enable it in one of four ways. First, you can pass it as a property of the JavaScript object argument which is passed to the function or procedure API directly, with a value of true. This will turn on auto-relink just for that call. You can also disable it, by setting autoRelink to false if it was already enabled by one of the global settings, e.g.

> ydb.function({function: 'version^v4wTest', autoRelink: true});

Second, you can enable it globally, for every thread, and for every call to the function (or procedure) API, by setting the same property in a JavaScript object passed to the open API, e.g.

> ydb.open({autoRelink: true});

Third, you can enable it globally, per-thread, for every call to the function (or procedure) API, by setting the same property in a JavaScript object passed to the configure API, e.g.

> ydb.configure({autoRelink: true});

Fourth, you can also enable it globally, for every thread, by setting the environment variable NODEM_AUTO_RELINK to 1, or any other non-zero number, e.g.

$ export NODEM_AUTO_RELINK=1
$ node function.js

or

$ NODEM_AUTO_RELINK=1 node function.js

Nodem's asynchronous APIs, do their work in a separate thread pool, pre-allocated by Node.js via libuv. By default, four threads are created, and will take turns executing each asynchronous call, including asynchronous calls from other APIs. Nodem supports setting a different value for the pre-allocated thread pool for asynchronous calls, in its open API, up to a max of 1024, in the latest versions of Node.js, e.g.

> ydb.open({threadpoolSize: 1024});

However, if your Node.js process executes any call asynchronously, from any API or module, before you open the database connection with Nodem, then the threadpoolSize property is ignored. So make sure you open the database connection first in any process, if you want to control how large the pre-allocated thread pool is.

NOTE: The Node.js core worker_thread API, which also allocates threads from the same worker thread pool in libuv, allows complete control of creating and destroying threads, and does not utilize the threadpoolSize (which just sets the libuv environment variable UV_THREADPOOL_SIZE) set in the Nodem open API.

YottaDB (and GT.M) changes some settings of its controlling terminal device, and Nodem resets them when it closes the database connection. By default, Nodem will restore the terminal device to the state it was in when the open call was invoked. Normally this is the desired option, however, if you wish to reset the terminal to typically sane settings, the close call allows this by setting the resetTerminal property to true, e.g.

> ydb.close({resetTerminal: true});

Nodem supports the Worker Threads API, for both synchronous and asynchronous calls. Since YottaDB and GT.M are single-threaded, opening and closing a connection to their database and runtime, should only be done once per process lifetime. Nodem's open and close APIs will only work when called from the main thread of the process. In order to work with the worker threads API, you should call the Nodem open API in the main thread before creating any worker threads, and you should call the Nodem close API in the main thread, after all the worker threads have exited. You will still need to make sure that you require Nodem in each worker thread, as well as the main thread, in order to have access to the Nodem API in each thread.

Nodem has a configure API, which will allow worker threads to change some per-thread database configuration options. It can be called from the worker threads, or the main thread, and will allow you to change per-thread configuration options as often as you like. There are four configuration options that are set per-thread. They can be set in the open API, by the main thread, before any other Nodem calls are made, or they can be set in the configure API, anytime you like, in the main thread, or in the worker threads. Those configuration options are: charset, mode, autoRelink, and debug.

Nodem has a transaction API, which provides support for full ACID transactions. It is only supported when running Nodem with YottaDB at this time. It requires, as its first argument, a JavaScript function, which takes no arguments, and which can contain other Nodem calls, nested transaction calls, or any JavaScript code. The JavaScript function will be run within a transaction by YottaDB. It will also be run synchronously, and every Nodem API that is called within the transaction must also be run synchronously. By default, transactions are run in serial mode (providing full ACID semantics), and no local variables are reset during transaction restarts. You can pass an optional second argument; a JavaScript object, with one or two properties. The properties are variables, an array of local variables that are reset to their values before the transaction started, whenever a transaction is restarted, and type, which if set to Batch (batch or BATCH will also work) will run the transaction in batch mode, (which does not provide durability, but does provide the rest of the ACID semantics). If variables has '*' as its only array item, then every local variable in the symbol table will be reset during a transaction restart.

In order to restart a transaction, pass the string 'Restart' ('restart', 'RESTART', or the tpRestart property will also work), as the argument to the return statement. In order to rollback a transaction, pass the string 'Rollback' ('rollback', 'ROLLBACK', or the tpRollback property will also work), as the argument to the return statement. Any other argument to the return statement will commit the transaction, including functions without a return statement. When you call a Nodem API within a transaction, make sure to check for returned errors, and return with 'Rollback' in that case. If any Nodem API within a transaction returns with an error code of YDB_TP_RESTART (a YottaDB restart code), or with an error code of YDB_TP_ROLLBACK (a YottaDB rollback code) make sure to return with the appropriate transaction message, 'Restart' or 'Rollback' respectively, or simply return with the YDB_TP_* error code directly. In order to make it simpler to test for restart and rollback error codes from the YottaDB transaction engine, when more sophisticated logic is desired, Nodem stores the restart code in the tpRestart property, and the rollback code in the tpRollback property, for convenience.

If you throw a JavaScript error inside of the transaction function, it will be written to standard error, and will cause a rollback operation to occur. If you handle it with a try-catch block, then what happens will depend upon how you handle it, and whether you throw another error, or return with a specific transaction processing message or not. Transaction code should be as short and simple as possbile, and should avoid calling any code with side effects, e.g.

> ydb.transaction(() => {
    let flag = ydb.get({global: 'v4wTest', subscripts: ['flag']});

    if (flag.errorCode === ydb.tpRestart) return 'Restart';
    if (!flag.ok) return 'Rollback';

    let data = ydb.get({global: 'v4wTest', subscripts: ['data']});

    if (data.errorCode === ydb.tpRestart) return 'Restart';
    if (!data.ok) return 'Rollback';

    if (data.data < 0) return 'Rollback';

    if (data.data < 10) {
        let increment = ydb.increment({global: 'v4wTest'});

        if (increment.errorCode === ydb.tpRestart) return 'Restart';
        if (!increment.ok) return 'Rollback';
    }

    let type = ydb.get({global: 'v4wTest', subscripts: ['type']});

    if (type.errorCode === ydb.tpRestart) return 'Restart';
    if (!type.ok) return 'Rollback';

    let test = ydb.set({global: 'v4wTest', data: type + ':' + data});

    if (test.errorCode === ydb.tpRestart) return 'Restart';
    if (!test.ok) return 'Rollback';

    return 'Commit';
});

Even though the transaction API runs synchronously, it is fully compatible with the Worker Threads API. By creating a new worker thread and running the transaction API, and any other APIs it calls in it, you can emulate an asynchronous pattern, as the running transaction will not block the main thread, or any of the other worker threads. For an example of this pattern, see the supplied transaction.js program in the examples directory.

Nodem has a procedure or routine API, which is similar to the function API, except that it is used to call M procedures or routines, which do not return any values. If the procedure API is called via a JavaScript object, then the object must contain the required procedure/routine property, set to the name of the procedure/routine. It may also contain an optional property, called arguments, which is an array of arguments to pass to the procedure/routine. It can also be called by-position, just like the function API. It also supports the autoRelink option, just as described in the function API, e.g.

> ydb.procedure({procedure: 'set^v4wTest', arguments: ['test', 5]});

or

> ydb.procedure('set^v4wTest', 'test', 5);

The lock API takes an optional timeout argument. If you do not set a timeout, it will wait to acquire the lock indefinitely. If you wish to come back from the call right away, if the lock is not available, simply pass a timeout argument of 0, e.g.

> ydb.lock({global: 'v4wTest', timeout: 5});

or

> ydb.lock({global: 'v4wTest', timeout: 0});

The kill API takes an optional nodeOnly argument. It can be set to true or false, defaulting to false. If set to true, then it will only remove the node that is passed to it; if set to false, then it will remove the node passed to it, and all of its children, or the full sub-tree, e.g.

> ydb.kill({global: 'v4wTest', nodeOnly: true});

or

> ydb.kill({local: 'v4wTest', nodeOnly: true});

The nodeOnly option is available when calling the kill API by passing arguments in a single JavaScript object, like above, but not when passing arguments by-position.

Nodem provides a built-in API usage help menu. By calling the help method without an argument, Nodem will display a list of APIs and a short description of what they do. Calling the help method with an argument string of one of those APIs will display more in-depth usage information for that method.

Nodem supports full M local symbol table manipulation with the current APIs. In order to use it, instead of defining a global property in your argument object, you define a local property. For APIs that support passing arguments by-position, you signify that you want them to work on a global, by using a ^ as the first character of the first argument, otherwise they are working on a local variable. For the get and set APIs, if the first character of the first argument is a $, then you are working with an intrinsic special variable (ISV). There is also a localDirectory API, that works the same way as the globalDirectory API, except that it lists the local symbols in the symbol table, rather than the globals in the database. One caveat is that you cannot manipulate any local variable that begins with v4w, as Nodem internally uses that namespace to implement the v4wNode.m integration routine. You can also call the kill API with no arguments, and it will clear the local symbol table. This functionality will allow you to call legacy M functions and procedures, without having to write M routine wrappers. Here is an example of using the local symbol table functionality to call a legacy API directly from Nodem. In this example, the local variable, 'U', needs to be set before this API is called, as it expects it to be defined already. You can also see how the local symbol table changes, after setting the required local variable, making the call, and then clearing the symbol table, e.g.

> ydb.localDirectory();
[]
> ydb.set({local: 'U', data: '^'});
{ ok: true, local: 'U', data: '^' }
> ydb.localDirectory();
[ 'U' ]
> ydb.procedure({procedure: 'AGET^ORWORR', arguments: [, 9, '2^0', 13, 0]});
{
  ok: true,
  procedure: 'AGET^ORWORR',
  arguments: [ <1 empty item>, 9, '2^0', 13, 0 ]
}
> ydb.localDirectory();
[ 'DILOCKTM', 'DISYS', 'DT', 'DTIME', 'DUZ', 'IO', 'U', 'XPARSYS' ]
> ydb.kill();
true
> ydb.localDirectory();
[]

Nodem supports calling functions and procedures with arguments passed by-reference, or by-variable, in addition to the standard passing by-value. This will allow someone who needs to interface Nodem with legacy M APIs that require using local variables in this manner, the ability to do so directly in Nodem, rather than having to write an M wrapper around the API, and calling that from Nodem. In order to use this functionality, you need to pass your arguments via a specially formatted object, in order to instruct Nodem that you wish to pass arguments differently than normal. This is necessary because if you tried to pass an argument by-reference or by-variable directly, Node.js will try to dereference it as a local JavaScript variable, and you would never be able to refer to the right symbol in the back-end M environment. The structure of the specially formatted object is simple. It contains a type property, which can be one of three values: reference, variable, or value; and it also contains a value property which contains the name you want to use when the type is reference or variable, and the actual data you want to pass if type is value. The value type is there for consistency, but you would normally just pass arguments by value directly, without resorting to this specially formatted argument object. Here is an example of how you could use this functionality, while calling a legacy M API, many of which require passing arguments in this fashion, e.g.

> ydb.set({local: 'U', data: '^'});
{ ok: true, local: 'U', data: '^' }
> const arg = {type: 'reference', value: 'LIST'};
undefined
> ydb.procedure({procedure: 'LISTALL^ORWPT', arguments: [arg, 'A', 1]});
{
  ok: true,
  procedure: 'LISTALL^ORWPT',
  arguments: [ { type: 'reference', value: 'LIST' }, 'A', 1 ]
}
> ydb.localDirectory();
[ 'LIST', 'U' ]
> ydb.data({local: 'LIST'});
{ ok: true, local: 'LIST', defined: 10 }
> ydb.nextNode({local: 'LIST'});
{
  ok: true,
  local: 'LIST',
  subscripts: [ 1 ],
  data: '1^ZZ PATIENT,TEST ONE^^^^ZZ PATIENT,TEST ONE',
  defined: true
}
> ydb.nextNode({local: 'LIST', subscripts: [1]});
{
  ok: true,
  local: 'LIST',
  subscripts: [ 2 ],
  data: '3^ZZ PATIENT,TEST THREE^^^^ZZ PATIENT,TEST THREE',
  defined: true
}
> ydb.nextNode({local: 'LIST', subscripts: [2]});
{
  ok: true,
  local: 'LIST',
  subscripts: [ 3 ],
  data: '2^ZZ PATIENT,TEST TWO^^^^ZZ PATIENT,TEST TWO',
  defined: true
}
> ydb.nextNode({local: 'LIST', subscripts: [3]});
{ ok: true, local: 'LIST', defined: false }

Fourth Watch Software endeavors not to make any breaking changes to APIs, but as Nodem is still in development, its interface may change in future versions.

If you have any questions or feature requests, email me at dlw@linux.com
To report any issues, visit https://github.com/dlwicksell/nodem/issues

• The Node.js server-side JavaScript runtime.
• The YottaDB implementation of M.
• The GT.M implementation of M.