arrays.txt

Please research the following methods:
map - Creates a new array from the existing array by calling a provided function on every element.
reduce - Executes a provided reducer function on every element of the array resulting in a single output.
filter - Creates a new array with all the elements that pass the test implemented by a provided function.
forEach - Executes a provided function once for each element.
sort - Sorts the elements of an array in place. Defaults to ascending order after converting elements to strings.
slice - Returns a shallow copy of a portion of the array into a new array from start to end, where start and end are array indexes.
pop - Removes the last element of the array and returns the removed element.
shift - Removes the first element of the array and returns the removed element.
push - Adds one or more elements to the end of an array;
unshift - Adds one or more elements to the start of an array
includes - Determines whether an array includes a certain value.
indexOf - Returns the first index of an element within an array, or -1 if none are found
every - Returns true if every element in the array satisfies the passed testing function.

Give a short description of what the method does, how it works, it's time complexity (if appropriate), and give three examples of it in action!

Questions to practice:

One:
Given a non-empty array of integers, return the result of multiplying the values together in order. Example:
[1, 2, 3, 4] => 1 * 2 * 3 * 4 = 24

const product = arr.reduce((prod, x) => prod * x);


Two:
You will be given an array of all the family members' ages, in any order.
The ages will be given in whole numbers, so a baby of 5 months, will have
an ascribed 'age' of 0. Return a new array with
[youngest age, oldest age, difference between the youngest and oldest age].

arr.sort((a, b) => a - b)
const data = [arr.shift(), arr.pop()];
data.push(data[1] - data[0])

Three:
Sum all the numbers of the array except the highest and the lowest element (the value, not the index!).
Example:
[ 6, 2, 1, 8, 10 ] => 16
[ 1, 1, 11, 2, 3 ] => 6

let sum = arr.sort((a,b) => a - b).slice(1, -1).reduce((acc, x) => acc + x);