Javascript Practice 71: JS Hero - Nested loops

 

Question: 

Write a function sum that calculates the sum of all elements of a two-dimensional array.

Example: sum([[1, 2], [3]]) should return 6.

Answer: 

function sum (arr) {

let arr2 = arr.flat(); 

return arr2.reduce((a, b) => a + b, 0);

}

> we declare a function sum

> it has 1 parameter 'arr'

> first we create a variable arr2

> we initialize it with the output we get by using the flat() method on 'arr' parameter

> the flat() method flattens an array with an option of 'depth' 

> you can pass in any levels of nesting with the flat () method

> once our array has been flattened, we then return our array with the reduce method

> the reduce method reduces the array elements to a single value

> we use the reduce method to find the sum of all numbers in our array