Strict mode

JavaScript's strict mode is a way to opt in to a restricted variant of JavaScript, thereby implicitly opting-out of "{{Glossary("Sloppy_mode", "sloppy mode")}}". Strict mode isn't just a subset: it intentionally has different semantics from normal code.

Strict mode for an entire script is invoked by including the statement "use strict"; before any other statements.

See also

• Strict mode
• Related glossary terms:
  • {{Glossary("Sloppy mode")}}