# 🧮 Crushing Numbers with `.reduce()` in JavaScript: From Totals to Real-Life Scenarios

🧠 What is .reduce()?

.reduce() is a method that reduces an array to a single value by applying a function on each element — one at a time — while keeping track of an accumulator.

Let’s see it in action:

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🔁 Basic Example: Adding Numbers in an Array

const myNums = [1, 2, 3, 4, 5];

const myTotal = myNums.reduce(function (acc, currVal) {
    console.log(`acc: ${acc} and currval: ${currVal}`);
    return acc + currVal;
}, 0); // 0 is the initial value of the accumulator

console.log(myTotal);

🧾 Output:

acc: 0 and currval: 1
acc: 1 and currval: 2
acc: 3 and currval: 3
acc: 6 and currval: 4
acc: 10 and currval: 5
15

🔍 acc keeps track of the total so far, and currVal is the current item from the array.

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✅ Arrow Function Version

const NewTotal = myNums.reduce((acc, curr) => acc + curr, 0);
console.log(NewTotal);

✔️ Cleaner and more readable for simple operations.

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🛒 Real-Life Use Case: Calculating Total Price in a Cart

Imagine you're building an e-commerce site, and you want to calculate the total price from the cart. Here's how:

const shoppingCart = [
    { itemName: "JS Course", price: 2999 },
    { itemName: "Py Course", price: 999 },
    { itemName: "Mobile dev Course", price: 5999 },
    { itemName: "Data Science Course", price: 12999 },
];

const priceToPay = shoppingCart.reduce((acc, item) => acc + item.price, 0);

console.log(priceToPay); // Output: 22996

🛍️ Instead of manually looping and adding, reduce() elegantly combines it all into one line.

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📌 Syntax Recap

array.reduce((accumulator, currentValue) => {
    // logic
    return updatedAccumulator;
}, initialValue);

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🔄 .reduce() vs .map() or .filter()

Method	Purpose	Returns
.map()	Transforms each item	New array
.filter()	Selects items based on condition	New array
.reduce()	Combines all items into one result	Single value

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🧠 Final Takeaway

.reduce() is powerful and versatile — from summing numbers to aggregating complex data. Once you get the hang of it, you’ll start reaching for it every time you need to calculate a total, build a string, or even transform arrays in advanced ways.

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