hmm, did a naive quick speed test. Man, this lib is extremely expensive... 500 times slower than doing the same comparison in vanilla JS

  const num= 74;
  ( (typeof num === 'number') && (num > -1 && num < 101) && (num % 2 === 0) && (num !== 32) )

compared to their first example:

  v8n().number().between(0, 100).even().not.equal(32).test(74);

Welcome to your average Javascript package -- does something trivial in the most over-engineered and expensive way imaginable.

Why Typescript and not just JS? Static typing for a dynamic language in a dynamic environment while using many npm libraries that can return anything unexpected? You'll need tons of testing to be sure.

Typescript is highly overrated, proper testing makes the difference, not Typescript IMHO. Btw, Typescript is Microsoft, just as Github is soon, and I really having a hard time to get rid of the aversion I have for that company.