javascript – Why is there a spec for sync and async modules?

by

This is a good question. It’s a subject that caused a lot of heated discussion in the Node community. To have a good understanding of what it’s all about you should read:

Now, answering your question – Why is there a spec for sync and async modules? Because some usecases prefer the synchronous loading of modules, like the server-side modules in Node.js where you want to load everything you need before you start serving requests, and some usecases prefer asynchronous loading of modules, like in the browser when you don’t want to block the rendering thread while you load the dependencies.

There is really no option for synchronous loading in the browser because it would make the browser not responsive.

You could argue that you might use asynchronous loading on the server but then you’d either have to return promises instead of modules by require() or it could take callbacks. Either way it would make any complex code that uses a lot of modules much more complicated.

Another issue is with the caching and mutation of the already loaded modules. With synchronous module loading using require you only load the
module once and any other calls to require for the same module in the entire code base (for that process) return a cached response, which is the same object every time. Any part of the code can modify that object and it is available to any other part of the code. Some usecases that use that feature would be much more complex to implement. Additionally the order of loading and executing code would be harder to predict.

To sum up the answer to your question, there are arguments for both ways of loading modules and neither of those ways is a clear winner for every scenario. Both are needed and both have some specs to standardize their behavior.

Read the articles that I linked for more detailed understanding.

More Related Contents:

  1. Is it an anti-pattern to use async/await inside of a new Promise() constructor?
  2. Understanding the Event Loop
  3. Callback after all asynchronous forEach callbacks are completed
  4. Are all javascript callbacks asynchronous? If not, how do I know which are?
  5. Asynchronous exception handling with bluebird promises
  6. How to return values from async functions using async-await from function? [duplicate]
  7. JavaScript, Node.js: is Array.forEach asynchronous?
  8. nodeJs callbacks simple example
  9. Best way to call an asynchronous function within map?
  10. How to avoid long nesting of asynchronous functions in Node.js
  11. Node JS Promise.all and forEach
  12. How to write asynchronous functions for Node.js
  13. Understanding Asynchronous Code in Layman’s terms
  14. How to wrap async function calls into a sync function in Node.js or Javascript?
  15. node.js async/await using with MySQL
  16. ‘await Unexpected identifier’ on Node.js 7.5
  17. Are all Node.js callback functions asynchronous?
  18. Understanding async/await on NodeJS
  19. using async await and .then together
  20. Node js socket explanation
  21. Asynchronous constructor
  22. Using mongoose promises with async/await
  23. How do you create custom asynchronous functions in node.js?
  24. Why is node.js asynchronous?
  25. Javascript Asynchronous Exception Handling with node.js
  26. How to use the ‘main’ parameter in package.json?
  27. Does an async function always need to be called with await?
  28. Properly batch nested promises in Node
  29. JavaScript asynchronous programming: promises vs generators
  30. Using Async waterfall in node.js

Leave a Comment