Joined May 2015
My stupid face

Jesse Harlin

Javascript Engineering, Application Architecture at Simiancraft
Javascript Engineering, Application Architecture
Norman, OK

This is a terrible tip and I'll explain why.

  • Javascript has functions as a first class citizen. each/forEach is only slower because it creates a lexical scope around each loop iteration. In practice this is usually what you want.
  • 9/10 times you really want .map. You're probably looping in order to transform data.
  • loops favor side effects over pure functions. this means reaching into other scopes, and unpredictability. .map and functional approaches are objectively easier to test
  • if you have code where you are iterating so much that a for loop performance over map is so significant, you probably need to download lodash anyways.
  • if you really, really really must loop. (note: you probably don't) do NOT evaluate length in the iterator!! that gets called every time!
  • and if you REALLY must loop a while with a -- decrementor is actually even faster. Following the guidelines of asm.js are even better than that..Again, you probably do not need this in everyday practice, the tradeoof for testability and readability is not usually worth it.

Don't use loops. Don't use each. Use pure functions with no side effects. Map, filter, reduce.

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