.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 that 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.
- All iterator methods take a callback function, which can be a pre-defined function, a function expression, or an arrow function.
If you want to challenge yourself:
- Define a callback function before you use it in a iterator.
- Chain two iteration methods on the same array.
- Use the optional arguments in an iterator to include the index or the entire array. (Check out MDN’s Array iteration methods page for more information)
.reduce()to take a multi-layered array and return a single layer array from scratch.