Find the average of all numbers in a given array
Let's say we wanted to write a function that calculates the average of all grades (including yours). We can do this in many different ways in JavaScript, but in this demo I will be showing you how to find the average using Higher-Order Functions and the "for" loop.
forEach loop
The forEach() method executes a provided function once for each array element.
const yourGrade = 88;
let classGrades = [
87, 68, 94, 100, 83,
78, 85, 91, 76, 87
];
// push `yourGrade` to the end of classGrades
classGrades.push(yourGrade);
console.log(classGrades);
function average(array) {
// initialize value of `sum`
let sum = 0;
// capture the length of the array
let arrayLength = array.length;
// loop through the array via forEach
array.forEach((grade) => {
return (sum += grade);
});
// formula to calculate average: sum / arrayLength
return Math.round(sum / arrayLength);
}
const avg = average(classGrades);
console.log(avg);
for loop
The for() loop iterates a specified amount of times, and does "something" that many times.
const yourGrade = 88;
let classGrades = [
87, 68, 94, 100, 83,
78, 85, 91, 76, 87
];
console.log(classGrades);
function average(array) {
// initialize value of `sum`
let sum = 0;
// capture the length of the array
let arrayLength = array.length;
// iterate over the array
for (let i = 0; i < array.length; i++) {
// add each element to the `sum`
sum += array[i];
}
// formula to calculate average: sum / arrayLength
/* since we are not pushing our grade to the array
using `array.push()`, we need to do a little bit of algebra
to add ourselves to the list */
return Math.round((sum + yourGrade) / (arrayLength + 1));
}
const avg = average(classGrades);
console.log(avg);
reduce
The reduce() method is quite similar to the forEach() method, but requires a lot less coding. :)
const yourGrade = 88;
let classGrades = [
87, 68, 94, 100, 83,
78, 85, 91, 76, 87
];
// push `yourGrade` to the end of classGrades
classGrades.push(yourGrade);
console.log(classGrades);
function average(array) {
// action to do for every value
const avg =
array.reduce((previousValue, currentValue) =>
previousValue + currentValue) / array.length;
return Math.round(avg);
}
const avg = average(classGrades);
console.log(avg);
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