Functional JS

I keep on forgetting some cool declarative methods in JS, so this is a reminder compilation for me to refresh my memory as I encounter them doing coding challenges.

Array.prototype.sort(compareFn). Mutates array "in place" after converting values to string and comparing UTF-16 code unit values. Values are sorted ascending. If you don't want to mutate the array, use toSorted. compareFn is called with a and b and should return a negative number if a is smaller than b, positive if a is bigger than b or 0 if they are the same. If compareFn is not supplied the array is sorted after comparing the values to their string form. More here.
Math.max(value1, value2, etc.) and Math.min(value1, value2, etc.). If the array has few elements, you can use it like Math.max(...array). It is best to use reduce:

const arr = [1, 2, 3];
const max = arr.reduce((a, b) => Math.max(a, b), -Infinity);

String.prototype.repeat(count). Repeats a string a count number of times. i.e. 'Hello'.repeat(3) return HelloHelloHello.
Array.prototype.some(cb) - returns true if one item in the array returns a truthy value when the callback is called upon or false otherwise. It stops iterating as soon as it find an element that returns a truthy value.
0 + true is 1 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unary_plus#usage_with_non-numbers
new Set([1,1,3,2,2,3,4]) will get rid of the duplicates and return [1,3,2,4] because a set can't have duplicates.
address.split('@').pop() will return the domain in an email even when there are 2 @s.

Regex stuff

/^\d*/ < match any series of digits at the start. You can then do string.match(/^\d*/) to find a prefix made up of digits only.
'string'.match(regex) will return the matches. If the g flag is used, it returns an array with the matches. If not, just the first match. i.e. '010010000110010101101100011011000110111100100001'.match(/.{1,8}/g) will return an array of bytes.
String.fromCharCode(charCode) returns the ASCII string attached to the charCode.