Javascript Practice 75: JS Hero - Functions call functions

 

Question: 

Write a function sum that takes an array of numbers and returns the sum of these numbers. Write a function mean that takes an array of numbers and returns the average of these numbers. The mean function should use the sum function.

Answer: 

function sum (arr) {

let totalSum = arr.reduce((acc,cv) => acc + cv);

return  totalSum; 

}; 

function mean (arr) {

let meanVal = sum(arr) / arr.length;

return meanVal;

}; 

> we declare a function 'sum'

> it has one parameter 'arr' 

> we declare a variable 'totalSum' 

> we use the reduce method to reduce the value in the array to 1 unit

> we also want to add each and every element of the array

> we use the accumulator and the current value to do that 

> it works like a snow ball, keeps accumulating the values from left to right in an array

> this accumulated amount gets stored in the 'totalSum' variable

> we then return the 'totalSum' variable at the end of the 'sum' function 

> we then declare another function 'mean' 

> it has one parameter 'arr' 

> we declare a variable 'meanVal' 

> we want to store the mean value / average of the numbers in an array in the 'meanVal' variable

> to get the average of the numbers, we need to add the numbers and divide it with the total numbers

> like this: 2 + 4 + 6 + 8 = 20; 20 / 4 = 5;

> in order to get the sum of all the elements in an array, we can use the function 'sum' that we created in this function 'mean' 

> like this: sum(arr)

> we then need to divide this number with the total number of elements in the array

> like this: sum(arr) / arr.length

> we store the result in the variable 'meanVal' 

> we return the variable 'meanVal' to get our answer