Using Array.reduce to sum a property in an array of objects

reduce-example.js

var accounts = [
  { name: 'James Brown', msgCount: 123 },
  { name: 'Stevie Wonder', msgCount: 22 },
  { name: 'Sly Stone', msgCount: 16 },
  { name: 'Otis Redding', msgCount: 300 }  // Otis has the most messages
];

// get sum of msgCount prop across all objects in array
var msgTotal = accounts.reduce(function(prev, cur) {
  return prev + cur.msgCount;
}, 0);

console.log('Total Messages:', msgTotal); // Total Messages: 461

thanks. Very good

@perdugames it works, thank you!

Thanks man this is good. But Hey @PrimozRome did you get that to work?

Yeah, It works, Thank you.

Thanks a lot.

It works on other key value, thanks

var items = [
    { name: 'Item 1', amount: 200, discount: 0.4 },
    { name: 'Item 2', amount: 16, discount: 0.2 },
    { name: 'Item 3', amount: 45, discount: 0.1 },
    { name: 'Item 4', amount: 30, discount: 0 }
];           
    var msgTotal = items.reduce(function(prev, cur) 
    {
         return prev + (cur.amount - (cur.amount * cur.discount) );
    }, 0); 
   document.write('Total of Discounted Items:', msgTotal);

this was super helpful, thanks

Genius!!

hey.
what if i have:
itemsInCart= [
{
name: "Suya",
price: 69,
qty: 3
},
{
name: "Matooke",
price: 46,
qty: 2
}
];
and i want to make a total bill of these items. any idea?
in fact the idea is like this: totabill=suya +matooke. that means price of suya times qty of suya plus price of matooke times qty of matooke. in real equation it's like this: totalbill=(suya price x suya qty)+(matooke price x matooke qty).
mathamatical form would be like this: total= ( 69x3)+(46x2)

so try to advise me bros

var itemsInCart= [ { name: "Suya", price: 69, qty: 3 }, { name: "Matooke", price: 46, qty: 2 } ]; var total = itemsInCart.reduce(function(prev, cur) { return prev +(cur.price * cur.qty); }, 0); document.write('Total of Cart Items:', total);

ok, i want to do totalbill by mentioning specific name. i mean, suya and matooke. i want a program to firstly track the name of item and go on with calculation.
so, my challenge is how i can do it with the reduce function.
i mean, if the program doesn't find suya and mattoke, it stops working.and most importantly, use ES6 syntax.
look at the apiendpoint https://randomapi.com/api/006b08a801d82d0c9824dcfdfdfa3b3c

var itemsInCart= [ { name: "Suya", price: 69, qty: 3 }, { name: "Matooke", price: 46, qty: 2 } ]; var total = itemsInCart.reduce(function(prev, cur) { return prev +(cur.price * cur.qty); }, 0); document.write('Total of Cart Items:', total);

thank u very much

ok, i want to do totalbill by mentioning specific name. i mean, suya and matooke. i want a program to firstly track the name of item and go on with calculation.
so, my challenge is how i can do it with the reduce function.
i mean, if the program doesn't find suya and mattoke, it stops working.and most importantly, use ES6 syntax.
look at the apiendpoint https://randomapi.com/api/006b08a801d82d0c9824dcfdfdfa3b3c

Thanks dude

Thanks bro

Hey, thanks for sharing this! Very helpful. Answers a burning question I've been working on for the last half hour. Thank you!

Thanks dude

Very nice! Thank you!

items = [
  { customer_id: 1, id: 1, sum: 123}
  { customer_id: 1, id: 2, sum: 321}
  { customer_id: 1, id: 3, sum: 213},
]
var total_sum = items.reduce(function(prev, cur) {
      return prev + cur.summ;
}, 0);

console.log(total_sum) -> `NaN` %(

Very nice. Thanks

Thank you!!

Simple and short... thanks

Great.

How to sum value only when the key 'name' that duplicate, sample:

var accounts = [
  { name: 'Blue', count: 2 },
  { name: 'Red', count: 3 },
  { name: 'Yellow', count: 4 },
  { name: 'Red', count: 5 }
];

And return:

var return = [
  { name: 'Blue', count: 2 },
  { name: 'Red', count: 8 },
  { name: 'Yellow', count: 4 }
];

@benwells @perdugames very clutch, thanks!

@everaldomatias have you found any solution to that please???

@James-n9ne4our i still haven't found the solution.

this is the genius solution!

In ES6: const msgTotal = accounts.reduce((prev, cur) => prev + cur.msgCount, 0);

Thanks dude!

Thanks - super useful!

Is it possible to use reduce if I have a calculation trough-out multiple properties like this:

var items = [
  { name: 'Item 1', amount: 123, discount: 0.1 },
  { name: 'Item 2', amount: 22, discount: 0.1 },
  { name: 'Item 3', amount: 16, discount: 0.2 },
  { name: 'Item 4', amount: 300, discount: 0 }
];

So I have to do something like this:

total = sum_all_items(amount - (amount * discount))

simplify it as total = sum_all_items(amount * (1 - discount))
OR
first, just make, discount = 1 - discount, and then, sum(amount * discount)

Banging. Nice one, mate.