Sum of array javascript for loop

I'm trying to find a way to sum all the numbers that have been added to an array. I believe this should work:

   var total = 0;

   for (var i  = 0; i < totalPrice.length; i++);

   total  += totalPrice[i];
   document.getElementById("displayPrice").innerHTML = total;

But total comes out as a NaN.

This is an example of my code in JSFiddle, if you add the item twice the value gets pushed into the array, what am I doing wrong with the for loop?

https://jsfiddle.net/bgv5s9re/2/

asked Oct 8, 2016 at 15:50

5

You could use brackets

  var total = 0;

   for (var i  = 0; i < totalPrice.length; i++){

      total  += totalPrice[i];

   }
   document.getElementById("displayPrice").innerHTML = total;

answered Oct 8, 2016 at 15:54

ScaisEdgeScaisEdge

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2

Get the Sum of an Array of Numbers #

To get the sum of an array of numbers:

1. Use the Array.reduce() method to iterate over the array.
2. Set the initial value in the reduce method to 0.
3. On each iteration, return the sum of the accumulated value and the current number.

Copied!
const arr = [5, 15, 45];

const sum = arr.reduce((accumulator, value) => {
  return accumulator + value;
}, 0);

console.log(sum); // 👉️ 65

The accumulator parameter is initially set to 0 because that's what we passed as the second argument to the reduce method.

On each iteration, we return the sum of the accumulator and the current array element.

An alternative and perhaps simpler approach is to use a for...of loop.

To get the sum of an array of numbers:

1. Declare a sum variable and initialize it to 0.
2. Use the for...of loop to iterate over the array.
3. On each iteration, reassign the sum variable to its current value plus the value of the current element.

Copied!
const arr = [5, 15, 45];

let sum = 0;

for (const value of arr) {
  sum += value;
}

console.log(sum); // 👉️ 65

The for...of loop allows us to iterate over an array.

Notice that we declared the sum variable using the let keyword. Had we declared the variable using const, we wouldn't be able to reassign it.

On each iteration, we reassign the sum variable to its current value plus the value of the current element.

You can also use a basic for loop to sum an array of numbers.

Copied!
const arr = [5, 15, 45];

let sum = 0;

for (let index = 0; index < arr.length; index++) {
  sum += arr[index];
}

console.log(sum); // 👉️ 65

This example achieves the same goal, but instead of using for...of we used a basic for loop.

How do you sum an array for a for loop?

How do you find the sum of all elements in an array in JavaScript?

How do you sum a loop in JavaScript?

Is there a sum () in JavaScript?