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Lesson 5 — Processing data
Fold a list into one number
Servers constantly turn lists into totals. reduce walks an array and carries an accumulator (a running result) from item to item. You give it a function (sum, item) => newSum and a starting value.
[1, 2, 3].reduce((s, n) => s + n, 0); // 6
Why it matters: cart totals, invoice sums and stats are all reduce.
Want it another way?
Task
Use reduce to add up the prices in the cart, so it logs total: 35.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledge
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