vm.SourceTextModule(code[,options]) function in Node.js

In this article, we will discuss the vm.SourceTextModule() function in Node.js. Before discussing this function, we must know about the Vm module in Node.js.

What is the Vm Module?

1. The vm module facilitates code compilation and execution in V8 Virtual Machine contexts. There is no security feature in the virtual machine module. Don't use it to launch untrusted apps.
2. JavaScript code can be built and executed immediately or it can be compiled, saved, and executed at a later time.
3. Many times, the code is utilized in a separate V8 context. It indicates that the global object of invoked code is different from that of invoking code.

What is the vm.SourceTextModule(code[, options]) function in Node.js?

The vm.SourceTextModule(code[, options]) function in Node.js creates an ECMAScript Module (ESM) from a JavaScript code string to allow dynamic and controlled execution of module-based scripts. It is a useful part of the virtual machine module for sandboxed environments and particular scripting needs. The options parameter allows us to specify identifiers, handle dynamic imports, and customize import.meta. Before the module may execute, it must be evaluated and linked (to fix dependencies). After that, the exported properties are accessible via module.namespace. Node.js 12.16.0 was the first version to contain it, while 16.0.0 was the stable version. It enables module execution in isolated or adjustable contexts in a secure and flexible manner.

Syntax:

It has the following syntax:

Parameters:

Code (string, required):

• The JavaScript source code for the module.
• The ECMAScript Module's code (such as import and export statements) must be authentic.

Options (object, optional):

It is an object of altering the behavior of the module, and some of these attributes include:

• Identifier: A unique string that serves as the module's identify; useful for debugging or reporting errors.
• Context: A virtual machine in the background. When the module is running, the context object.
• initializeImportMeta: It is an option to customize imports.meta object.
• importModuleDynamically: This module hook is used to handle dynamic import() expressions.

Key points:

The process of evaluation:

• The module must be linked using module.link() before module.evaluate() may be used. The link stage fixes all dependencies (imported modules).
• After review, the module's exports are accessible via Module.namespace.

Fixing Errors: If the code has any syntax errors or issues occur during the linking or evaluation process, an exception will be made.

Customization ability:

• With the importModuleDynamically option, the import() calls can be dynamically managed.
• Custom properties that are imported with the initializeImportMeta option, the import.meta can be set.

Utilization Example:

• The vm.SourceTextModule is the ideal option for safely running ECMAScript modules in controlled environments.

Example code:

Process:

• The code should be executed in an ESM environment.
• For the package.json file, add "type": "module" or change the file extension to.mjs.
• Use import to bring in the VM module.

Output:

 
"Hello, world!"
"Hello, Alice!"   

Save the file by the name index.mjs.

To run the above code use the command:

• node index.mjs

Explanation:

• Comprehension of the Code: Export statements are used in the JavaScript code to define module exports.
• The module.SourceTextModule creates a module instance using the code.
• Sign up for the module: The module.link() function is used to resolve imports for modules. This example does not include any imports; however, you may change the handler if needed.
• Examine the module: This step involves running the code, which makes its exports accessible.
• Open Exports: namespace accesses exports after evaluation.

Conclusion:

In conclusion, the vm.SourceTextModule in Node.js provides a powerful way to create and execute ECMAScript Modules in a controlled environment dynamically. It allows developers to describe JavaScript modules as strings, which gives them flexibility for tasks like testing, sandboxed execution, and custom scripting. Code can be executed modular and reusable by using linking and evaluation to access the module's exports programmatically. It provides advanced possibilities for safely running code with exact control over imports and context, even if its proper execution requires an ESM environment. This feature enhances Node.js's ability to construct modern JavaScript applications in flexible and dynamic environments.