Getting started #5139
Description
Node.js Version
v24.14.0
NPM Version
v11.9.0
Operating System
Win11 25H2
Subsystem
constants
Description
I'm new to Node.js. All my previous experience with JavaScript is when it is browser-hosted.
Is there a node program control that disables the variable declaration requirement, so that variables can be implicitly declared when an assignment occurs (similar to browser-hosted implementations)?
Minimal Reproduction
file="one";
vs.
const file="one"; or var file="one";
Output
file="one";
^
ReferenceError: file is not defined
at file:///C:/Users/Public/npm/Sample-Const.js:1:5
at ModuleJob.run (node:internal/modules/esm/module_job:430:25)
at async onImport.tracePromise.proto (node:internal/modules/esm/loader:661:26)
at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:101:5)
Node.js v24.14.0
Before You Submit
- I have looked for issues that already exist before submitting this
- My issue follows the guidelines in the README file, and follows the 'How to ask a good question' guide at https://stackoverflow.com/help/how-to-ask
Activity
avivkeller commentedon Mar 6, 2026
Yes. Node.js, and all JavaScript for that matter, either runs in strict or non-strict mode. When running in strict mode, variables must be explicitly declared with their keywords. In non-strict mode, this is not a requirement.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode#invoking_strict_mode