Reduce()

Given data:

const items = [
    { name: 'Bike',     price: 100  },
    { name: 'TV',       price: 200  },
    { name: 'Album',    price: 10   },
    { name: 'Book',     price: 5    },
    { name: 'Phone',    price: 500  },
    { name: 'Computer', price: 1000 },
    { name: 'Keyboard', price: 25   }
]

Reduce method

This is like wanting to get a sum of all the prices of your items that meet certain conditions.

Unlike the other methods the reduce method has 2 arguments and the first of which has to be the aggregate value holder

---

const total = items.reduce((currentTotal, item) => {
    return item.price + currentTotal
}, 0)

console.log(total)

Result:

1840

we want to get a sum of all prices so we run the array method and for each item in items we pass the item and a local variable in the arrow function to the function body.

at then end of the arrow function is a second argument for the reduce method which is where the currentTotal value should start. We probably want a total to start at 0 so that's where it is set to.

this is like a for loop using item = item + newItem

so for each item passed to the function body, you also have the current running total passed as well. The items iteratively get returned and added to the currentTotal and then ultimately the currentTotal variable is returned giving you the sum of the array object's prices