.forEach()is used to execute the same code on every element in an array but does not change the array and returns
.map()executes the same code on every element in an array and returns a new array with the updated elements.
.filter()checks every element in an array to see if it meets certain criteria and returns a new array with the elements that return truthy for the criteria.
.findIndex()returns the index of the first element of an array which satisfies a condition in the callback function. It returns
-1if none of the elements in the array satisfies the condition.
.reduce()iterates through an array and takes the values of the elements and returns a single value.
If you want to challenge yourself:
.reduce()to take a multi-layered array and return a single layer array from scratch.