Benefits of "Use Strict" in JS

javascript use-strict
TMacGyver picture TMacGyver · Feb 16, 2014 · Viewed 11.1k times · Source

What are the additional benefits of "use strict" other than preventing bad coding? For instance, does it allow the script to run faster because the interpreter knows the code its optimized?

Answer

jfriend00 picture jfriend00 · Feb 16, 2014

There are a zillion benefits to strict mode, but since you asked specifically about performance, not just the good coding benefits, here's what MDN says about that:

Strict mode makes several changes to normal JavaScript semantics. First, strict mode eliminates some JavaScript silent errors by changing them to throw errors. Second, strict mode fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode. Third, strict mode prohibits some syntax likely to be defined in future versions of ECMAScript.

So as you asked, according to the Firefox folks at MDN, strict mode code can sometimes run faster.

For general benefits of strict mode, see What does "use strict" do in JavaScript, and what is the reasoning behind it?

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