Practice Set - Functions as Chunks of Reusable Code

by Ken Sprague

HTML

<p>There is one part to this practice set. This exercise is designed to give you practice creating a function from scratch, including accepting arguments and returning a value.  </p>
<p>You will write a function that calculates the average of numbers in a given array.  See the comments in the Javascript for more guidance. Your function will have to: <ol>
<li>iterate over the array that was passed in as an argument (think <i>for</i> loop)</li>
<li>add each value to a sum as it iterates</li>
<li>when the loop is complete, divide the sum by the length of the array</li>
</ol>
For this part, you may assume that the array contains only numbers. </p>
The output will appear here:
<ul>
<li>Average 1: <span id="average1"></span></li>
<li>Average 2: <span id="average2"></span></li>
<li>Average 3: <span id="average3"></span></li>
</ul>

<p>Remember that code can be awfully difficult to debug in JSFiddle. If you get frustrated trying to find a bug as you write your solution, you may want to copy this example to a local version on your computer to work it out, then paste it back in to JSFiddle.</p>

JavaScript

"use strict";

// three arrays we'll calculate averages
var scoresArray1 = [87, 93, 69, 96, 77, 81];
var scoresArray2 = [56, 82, 71];
var scoresArray3 = [99, 97, 91, 89, 92];

// You'll write a function here called calculateAverage, which will
//  accept one argument - the array, and return the average of the 
//  numbers in the array. 
function calculateAverage(arr){
	var sum=0; 
  for (var i=0; i<arr.length; i++){
     	sum+=arr[i];
   }
   console.log("Sum is " + sum + " and i is "+i);
   return sum/i;
}

/// IF I WANTED TO VALIDATE INPUT ON THIS FUNCTION (MAKE
//   SURE THAT WE'RE DEALING WITH ONLY NUMBERS), I COULD
//   add a parseInt() and a test, as we do in this week's 
//   Practice Set Assignment #2
function calculateAverage2(arr){
	var sum=0, num; 
  for (var i=0; i<arr.length; i++){
     	num = parseInt(arr[i]);
      if (num){	
      	sum+=num;
      }
   }
   console.log("Sum is " + sum + " and i is "+i);
   return sum/i;
}


//here we're calling your function on the three arrays and outputting the result
document.getElementById("average1").innerHTML = calculateAverage2(scoresArray1);
document.getElementById("average2").innerHTML = calculateAverage2(scoresArray2);
document.getElementById("average3").innerHTML = calculateAverage2(scoresArray3);