JavaScript sum function

Question

I have stacked in the sum of an array. The code is bellow

function User(name,email) {
        this.name = name;
        this.email = email;
        this.cartAmount = [];
        this.total = 0;
}
User.prototype = {
        constructor: User,

        addCart: function(mrp){
            this.cartAmount.push(mrp);
        },

        changeEmail: function(newmail){
            this.email = newmail;
        },

        showCart: function() {
            var cart = this.cartAmount.length >0 ? this.cartAmount.join("tk,") : "No product in the cart";
            return this.name+" has "+cart+" in his cart.";
        },

        intotal: function(){
            for(var n in this.cartAmount){
                this.total += this.cartAmount[n];
                return this.total;
            }
        }
    };
    athar= new User("Athar Jamil", "[email protected]");
    console.log(athar.name);
    athar.changeEmail("[email protected]");
    console.log(athar.email);
    athar.addCart(20);
    athar.addCart(50);
    athar.addCart(80);
    console.log(athar.intotal());

It shows me only 20 as the result of the sum. What is the problem?

Return is perform early man!

F.bernal
– F.bernal

2016-06-28 08:35:20 +00:00
Commented Jun 28, 2016 at 8:35 — F.bernal
– F.bernal, Commented Jun 28, 2016 at 8:35
How is this a Hot Network Question?

Stack Exchange Broke The Law
– Stack Exchange Broke The Law

2016-06-28 11:24:27 +00:00
Commented Jun 28, 2016 at 11:24 — Stack Exchange Broke The Law
– Stack Exchange Broke The Law, Commented Jun 28, 2016 at 11:24

haim770 · Accepted Answer · 2016-06-28 08:31:58Z

11

You're returning too early, hence your for loop runs only once and returns the first item in the cart.

Try this instead:

 intotal: function(){
    for(var n in this.cartAmount){
        this.total += this.cartAmount[n];
    }

    return this.total;
    }

answered Jun 28, 2016 at 8:31

haim770

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Comments

Michał Perłakowski · Accepted Answer · 2016-06-28 12:39:11Z

7

Using Array.prototype.reduce() you can simplify that function a lot:

intotal: function() {
  return this.cartAmount.reduce((a, b)=> a + b)
}

From MDN:

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

Here you pass an arrow function to the reduce method, which takes two arguments: a and b, and returns sum of them.

answered Jun 28, 2016 at 12:39

Michał Perłakowski

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Comments

Nisse Engström · Accepted Answer · 2016-06-28 13:36:07Z

7

Do not use this.total for that. If you call this method several times, your total will increase each time you call it. You should at least put a this.total = 0 at the top of your method.

I personally would have written it like this instead :

intotal: function(){
    var out = 0;
    for(var n in this.cartAmount){
        out += this.cartAmount[n];
    }

    return out;
}

edited Jun 28, 2016 at 13:36

Nisse Engström

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answered Jun 28, 2016 at 8:44

xurei

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Comments

Meharaj M · Accepted Answer · 2016-06-28 08:40:00Z

4

intotal function returning the first element of cartAmount array. Place the return statement of intotal function outside of for loop.

answered Jun 28, 2016 at 8:40

Meharaj M

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Comments

Pramod Kharade · Accepted Answer · 2017-10-08 07:04:13Z

0

function sum(){
 var args = Array.prototype.slice.call(arguments);
 return args.reduce(function(pre,curr){
   if(!isNaN(curr)){
     return pre+curr;
   }
   else
   {
    throw Error("Non-Numeric arguments"+curr);
   }
},0)
}
    var result = sum(12,13,14); //pass any number of parameter to sum
    alert("Sum Is:"+result);

edited Oct 8, 2017 at 7:04

answered Oct 8, 2017 at 6:13

Pramod Kharade

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Comments

Montasir Mirghani · Accepted Answer · 2021-12-30 23:54:56Z

0

https://www.npmjs.com/package/mnjs

First import sum function from mnjs package

<script src="https://cdn.jsdelivr.net/npm/mnjs/browser/index.js"></script>

or

const { sum } = require('mnjs')

or

import { sum } from 'mnjs'

Then use sum function as follow:

const cartAmount = [1, 4, 2]

sum(cartAmount)   // returns 7

https://runkit.com/dr-montasir/mnjs-sum-function

answered Dec 30, 2021 at 23:54

Montasir Mirghani

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