Javascript

Async & Performance

Contents

• Async behaviour
• Callback
• Promise
• Generator
• Async / await
• Performance

Callbacks

• A function for future call
• Bad parts
  • Callback hell
  • Early call
  • Not called at all
  • Called few or many times
  • Fail to pass parameters
  • Swallow error/exceptions

Promises

• ES6 Native type
• Solves trust issues of callbacks
• Many good reasons to use it

Generators

• yield keyword
• python has also generators
• Pausing execution of function
• Increase iteration capabilities

async / await

• Promise  + generator
• Better and readable code
• Looks like sync but async

Performance

• https://jsperf.com/
• Donald Knuth:
  • "Premature optimization is the root of all evil."
• If you really don't sure about your need to optimize, simply don't do it

Web Workers !?

Look if you curious