JavaScript, Using a for loop to calculate the sum of all the values within an array

Question

I just starting using JavaScript a couple weeks ago and still struggling a bit. I need to create a loop that calculates the sum of all values coming from a votes array in a separate .js file.

The function has a single parameter, votes, representing one of the five vote arrays (vote1 through vote5). Add the following commands to the function:

a. Declare a variable named total, setting its initial value to 0.

b. Create a for loop that loops through each of the items in the votes array, adding that item’s value to the total variable.

c. After the for loop is completed, return the value of the total variable from the function.

Heres my html file.

<script>
    function totalVotes()
    {
        var total = 0;

        for (i=0; i < votes.length; ++i)
            {
                total += votes[i];
            }
            return total;
    }

</script>

You will want to learn about objects and properties, to use them as a structure instead of those many variables. Also, array and object literals. — Bergi
– Bergi, Commented Jul 12, 2017 at 3:45
Your loop is fine. All your code is missing is the declaration of votes as a parameter of the function, and the actual call (e.g. totalVotes(votes3)). — Bergi
– Bergi, Commented Jul 12, 2017 at 3:47
Be careful about asking StackOverflow for your homework questions. If you post something directly from here you will almost certainly be "asked" about it by a teacher. Your code in the HTML is almost correct for calculating totals, you should say var i = 0 or let i = 0 instead of i=0. — zetavolt
– zetavolt, Commented Jul 12, 2017 at 4:03

Nishi Gaba · Accepted Answer · 2017-07-12 03:51:20Z

10

You can use reduce Method of array. Reduce Method gives concatenated value based on elements across the Array. For Example :

const sum = [1,2,3].reduce(function(result,item) {
 return result + item;
}, 0);
console.log(sum);

The above code gives the output 6 that is the sum of given array. You can check other methods of array on my Gist: Iterate_Over_Array.js

answered Jul 12, 2017 at 3:51

Nishi Gaba

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Comments

Richard.Davenport · Accepted Answer · 2017-07-12 03:59:18Z

4

You just need to pass in the array you want to iterate over:

var vote1 = [45125, 44498, 5143]

function totalVotes(votes) {
  var total = 0;
  for (var i = 0; i < votes.length; i++) {
    total += votes[i];
  }
  return total;
}

// better alternative
function tallyVotes(votes) {
  return votes.reduce((total, vote) => total + vote, 0);
}

console.log('for loop: ', totalVotes(vote1));
console.log('reduce: ', tallyVotes(vote1));

answered Jul 12, 2017 at 3:59

Richard.Davenport

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Comments

Vaibhav Shah · Accepted Answer · 2017-07-12 04:02:20Z

I would suggest to create Javascript Object instead of array of different properties.If you use Object then you will have to create Array of Objects with following structure -

var first_object = {
     'name':"Jeffrey Hart",
     'party':"D",
     'race':"1st Congressional District",
     'vote':"45125"
}

You will create object for each record and use Arrays.push to add into your array. Lets assume array is records, then use

records.push(first_object)

After Adding all the records then you will have arrays of Objects now you can tracer through it with simple forEach loop

var total = 0;
records.forEach( function (record)
{
    total+= record.vote;
});

If you are new to Javascript I would recommend to read

JavaScript: The Good Parts By Douglas Crockford

http://shop.oreilly.com/product/9780596517748.do

STA · Accepted Answer · 2021-02-27 11:27:57Z

1

You can add the numbers like below

let total = 0;
for (let i = 0; i < this.state.seatArray.length; i++) {
    total += total + parseInt(this.state.seatArray[i].price);
}

Thank you

edited Feb 27, 2021 at 11:27

STA

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answered Feb 27, 2021 at 6:11

Rahul karkande

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Comments

Arvind Chourasiya · Accepted Answer · 2020-12-02 12:26:27Z

0

You can add the numbers like below

for(let i = 0; i < product.length; i++)
 {
   var count1=+product[i].Pending;
   var count2=+product[i].Competed;
   this.totalCount=this.totalCount+(+count1)+(+count2);
}

Declare totalCount globally on top totalCount:number=0;.

answered Dec 2, 2020 at 12:26

Arvind Chourasiya

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