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Editorial Team
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Asked: 2026-05-27T10:05:34+00:00

Reading about ECMAScript 5’s strict mode I learn that: Certain language functions are so

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Reading about ECMAScript 5’s strict mode I learn that:

Certain language functions are so pervasive that performing runtime
checks has considerable performance cost. A few strict mode tweaks,
plus requiring that user-submitted JavaScript be strict mode code and
that it be invoked in a certain manner, substantially reduce the need
for those runtime checks.

Some of those tweaks could be:

  • Never use null/undefined as first argument in a call/apply method.
  • Do not create new globals variables inside a function.

Questions:

  1. Are there some JavaScript frameworks written in strict mode? So we can trust that our “strict” code will not be wasted?

  2. Should I start paying attention to strict mode no matter what? I mean is it blindly adopted as a good practice?

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1 Answer

  1. Editorial Team

    1. Yes, most of the frameworks already started to use strict mode. Maybe not complete yet but in the close distance. John Resig:

      All that being said, I’m fairly certain that jQuery is ES5-Strict compatible right now. Once an implementation of the language is made available (so that that premise may be tested) I’ll happily switch jQuery over to working exclusively in strict mode.

    2. It is recommended to use, but not required. If you start to use strict mode now, you will get used to it and therefore you will be ready for the new standard.

    More aboute strict mode:

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