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JavaScript

Posted by Thomas Dugan
Thomas Dugan
8,021 Points

Why does ```prices.forEach(price => { total += price; });``` work? We haven't defined 'price'

We have defined 'prices' but not 'price'. I want to understand why this solution works.

Trent Stenoien
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Trent Stenoien
Full Stack JavaScript Techdegree Graduate 21,632 Points

The 'forEach' method of arrays takes a function with up to 3 parameters: current value ('price' here), index, and the array itself. So price is simply a given value within the array. Another way to write that function is as follows:

prices.forEach( function(price) {total += price;} );

This article explains forEach() in more detail and might be helpful. https://www.w3schools.com/jsref/jsref_forEach.asp

1 Answer

Henrik Christensen
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Henrik Christensen
Python Web Development Techdegree Student 38,322 Points
Henrik Christensen
.a{fill-rule:evenodd;}techdegree
Henrik Christensen
Python Web Development Techdegree Student 38,322 Points

Each item in prices will be named price when it goes through the forEach

const prices = [5, 12, 42];

prices.forEach(price => { total += price; });

// round 1:
// prices[0] is now called 'price' and added to total

// round 2:
// prices[1] is now called 'price' and added to total

// round 3:
// prices[2] is now called 'price' and added to total

I hope this makes some kinda sense :-P