What Does 'use strict' Do in JavaScript, and Why Should I Use It?

Diving into the Quirks of "use strict" in JavaScript: Understanding Its Impact and Relevance

Discovered in the depths of JSLint's scrutiny, a cryptic error message regarding "use strict" sparked curiosity. What does this statement do in JavaScript, and what's the rationale behind it?

The Purpose of "use strict"

Introduced in ECMAScript 5, "use strict" activates a "strict mode" for your code. This mode enhances the reliability of your program by imposing additional constraints, proactively detecting and preventing potential errors.

Implied Functionality

Within strict mode, several actions become prohibited or subject to stricter validation. These enhancements include:

• Prohibiting declarations of duplicate variable names in the same scope.
• Preventing assignments to read-only properties.
• Restricting access to global variables without explicit declarations.
• Disallowing the use of certain "confusing or poorly thought-out" features, as noted in John Resig's insightful article.

Scope Control

You can apply strict mode to an entire file or confine it to specific functions using the "use strict" directive within the function body. This selective approach allows you to blend old and new code, ensuring compatibility.

Browser Compatibility

Major browsers now fully embrace strict mode. Its support extends to all modern browsers, including Chrome, Firefox, Edge, and Safari.

Relevance Today

"use strict" remains a valuable tool in contemporary JavaScript development. It fosters cleaner code, enhances reliability, and steers developers away from potential pitfalls. As ES6 modules enforce strict mode natively, it's a recommended practice to adopt it for all your code to ensure consistency and avoid errors.

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