The case for Immutability

[nelsonic]

• good intro: http://www.sitepoint.com/immutability-javascript/ by @cjohansen ( ... but does not explain why the immutability makes writing the application easier ... )
• Predictable State Container: http://www.youhavetolearncomputers.com/blog/2015/9/15/a-conceptual-overview-of-redux-or-how-i-fell-in-love-with-a-javascript-state-container
• Immutable Data Structures and JavaScript http://jlongster.com/Using-Immutable-Data-Structures-in-JavaScript by @jlongster
• The Dao of Immutability: https://medium.com/javascript-scene/the-dao-of-immutability-9f91a70c88cd#.qjyhys72r by @ericelliott
• If immutable objects are good, why do people keep creating mutable objects? (discussion): http://programmers.stackexchange.com/questions/151733/if-immutable-objects-are-good-why-do-people-keep-creating-mutable-objects
• http://facebook.github.io/immutable-js/ do we need a module for this...?
• Lee Byron on Immutable.js https://www.youtube.com/watch?v=kbnUIhsX2ds

[nelsonic]

@rjmk can you please explain why immutability in JS leads to a performance improvement even as Memory Consumption _increases_?

[ericelliott]

Immutability using data structures such as those provided by Mori.js create trie structures which share common content between old and new versions of the data, so memory consumption may not be as bad as you think.

Immutability can also give you huge performance optimization opportunities, especially where it's necessary to compare changes against two different deeply nested trees (for example, the React virtual DOM vs actual DOM diff).

Using immutable data structures, the diff check is literally an identity check -- about as fast as a comparison gets.

Using mutable trees, you have to traverse the whole tree and compare each node just to find out whether or not anything has changed.

There are lots of other advantages to immutability, including enabling great features like unlimited undo/redo, history shuttles, and even time-travel debugging.

Immutability also adds a lot of guarantees that make understanding and debugging software easier, and completely eliminates entire classes of code and potential bugs.

[iteles]

@NataliaLKB You were telling me about your recent learnings on mutable and immutable objects on Saturday! Was just wondering if you have anything to add on what you've learnt :wink:

[NataliaLKB]

I agree with everything @ericelliott has said so far. Especially the last line.

Immutability also adds a lot of guarantees that make understanding and debugging software easier, and completely eliminates entire classes of code and potential bugs.

Even if memory consumption increases, it is entirely worth it for all the other benefits

[rjmk]

Agree with @ericelliott and @NataliaLKB. Especially Natalia's last comment.

Especially the last line.

Immutability also adds a lot of guarantees that make understanding and debugging software easier, and completely eliminates entire classes of code and potential bugs.

Even if memory consumption increases, it is entirely worth it for all the other benefits