kb/data/developer.mozilla.org/en-US/docs/Glossary/Sloppy_mode-0.md

title	chunk	source	category	tags	date_saved	instance
Sloppy mode - Glossary | MDN	1/3	https://developer.mozilla.org/en-US/docs/Glossary/Sloppy_mode	reference	web, html, css, javascript, documentation	2026-05-05T05:45:28.987432+00:00	kb-cron

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1. Glossary
2. Sloppy mode

Sloppy mode

ECMAScript 5 and later let scripts opt in to a new strict mode, which alters the semantics of JavaScript in several ways to improve its resilience and make errors more understandable. The normal, non-strict mode of JavaScript is sometimes referred to as sloppy mode. This isn't an official designation, but you are likely to come across it if you spend time doing serious JavaScript code.

In this article

• See also

See also

• "Strict Mode" in chapter 7 ("JavaScript Syntax") in the book Speaking JavaScript.