It's always good to know how much time code needs to be executed. Today I learned there is a more precise way than using the Date object.
Today I discovered that await is more flexible than I thought because it doesn't work only on promises.
In ES6 the static method isNaN was added to the Number prototype. It looks the same behaves slightly different...
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'.