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let slows down performance by 5 times #5815

@AlekseyMalyshev

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@AlekseyMalyshev

I wrote this simple performance test recently.

There are two versions of JavaScript:

euler35/euler35.js
euler35/euler35-es6.js

The only difference is that es6 contains "use strict"; on top and uses let instead of var. This simple change however decreased ES6 performance by more than 5 times! I do not believe this should be the case. Full details are here.

  • Version: v5.9.0
  • Platform: arwin Alekseys-MBP 15.3.0 Darwin Kernel Version 15.3.0: Thu Dec 10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64 x86_64

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