In ES6 the static method isNaN was added to the Number prototype. It looks the same behaves slightly different...
Topic: JavaScript โ Page 21
I learned about an edge case in 'Array.prototype.indexOf' which is fixed in 'Array.prototype.includes'
I learned how to compare strings in a sane manner using 'String.prototype.localCompare'.
I learned that the IntersectionObserver constructor allows more than one threshold value.
I learned how the Unicode mode in JavaScript regular expression helps you counting code points.