# Strict Mode
 
Strict mode is an opt-in variant of JavaScript that enforces stricter parsing and error handling. It is enabled by adding `"use strict"` at the top of a file or function. Strict mode prevents the use of undeclared variables, disallows duplicate parameter names, and makes `this` undefined in functions called without a context, among other restrictions.

Visit the following resources to learn more:

- [@article@Strict mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode)
- [@article@Strict mode in JavaScript](https://javascript.info/strict-mode)