I don't understand how the sum of prices was done

Question

const prices = [6.75, 3.10, 4.00, 8.12];
let total = 0; 
prices.forEach(price => {
   total += price;
});
console.log(total);
Where does that ''price'' we are adding to the total let variable come from?
Thanks in advance

Dave StSomeWhere · Accepted Answer

It is being defined at it's first occurrence, as part of the Arrow Function (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions)
I think of it the same as when I define a variable name for function parameter. Then, that variable name is used within the function scope. It is just simplified with the arrow function syntax.
Like:
javascript
anonFunction = function(price) {
    // code goes here - and you can use price
}

Is that what you were questioning?

Daniel Boisselle · Answer

```javascript
const prices = [6.75, 3.10, 4.00, 8.12]
let total = 0
// forEach is a method that takes an anonymous function
// and invokes it over each value in the array
// where currentPriceValue is just an arbitrary placeholder for the current value
// this function can take a second argument that will also represent the index
// It will start at 0 up until the last index which is 3
prices.forEach(function(currentPriceValue, index) {
  console.log(Current total: ${ total} current price: ${currentPriceValue} at index ${index})
  total = total + currentPriceValue 
  // the line above we reassign the current value of total and add it to the current price
  console.log(This is the new total ${total})
})
// fat arrow syntax
price.forEach(price => total += price)
// this is shorthand for the function above, without the index paramater
// try running this code for yourself in a treehouse workspace or repl.it
```

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Sergio Leon

Sergio Leon

I don't understand how the sum of prices was done

2 Answers

Dave StSomeWhere

Dave StSomeWhere

Daniel Boisselle

Daniel Boisselle