Lazy Evaluation in JavaScript with Generators, Map, Filter, and Reduce

[utterances-bot]

Lazy Evaluation in JavaScript with Generators, Map, Filter, and Reduce

A simple wrapper class in JavaScript for map, filter, and reduce

https://nestedsoftware.com/2018/02/27/lazy-evaluation-in-javascript-with-generators-map-filter-and-reduce-36h5.21002.html

[jasonmcaffee]

Interesting challenge! I think I have an approach that is a bit more succinct: https://codepen.io/jasonmcaffee/pen/ZEpeQBq?editors=0010

[nestedsoftware]

Thanks! I did find an issue with the implementation you provided - if a generator function is provided as a starting input instead of an array, the code will loop forever.

[david-wagstaff]

reduce((a,v) => a + v)

1. I've been using longer variable names, and I instantly adopted yours. So much easier to read.
2. Half the time you use num and half the time you use n. It made me pause wondering if there was some meaning.
3. Why stop at reduce? Do sum().
4. Since I use some callback functions so much, I now just use their names add = (a,v) => a + v. Same with isEven = n => n%2==0
5. I like not having to supply the accumulator like you did, but I've been burned too many times with Uncaught TypeError: Reduce of empty array with no initial values So now I always include the accumulator now, e.g. [1,3,5].filter(isEven).reduce(add, 0) is safe.

Hey, sorry for bikeshedding on one line. I learned a ton, and I'll definitely come back to read this page again.

[nestedsoftware]

@david-wagstaff, thanks for your kind comment! The use of n vs num was not really intentional. While I think it's okay to use short variable names for simple pieces of code, and especially in lambda functions, it's also not recommended to overuse them. Having descriptive names is usually a good thing.