Q231- write real time Implementation examples of array methods

Below are real-life, practical implementation examples of the most commonly used JavaScript array methods, explained with everyday scenarios you actually use in real projects (React, Node.js, APIs, etc.).

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✅ 1. map() – Transform Data

Use Case: Convert product prices from INR → USD

const products = [
  { name: "Laptop", price: 50000 },
  { name: "Phone", price: 20000 }
];

const pricesInUSD = products.map(p => ({
  ...p,
  priceUSD: (p.price / 83).toFixed(2)
}));

console.log(pricesInUSD);

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✅ 2. filter() – Get Only Matching Items

Use Case: Show only active users

const users = [
  { name: "Teekam", active: true },
  { name: "Aman", active: false }
];

const activeUsers = users.filter(u => u.active);

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✅ 3. reduce() – Calculate a Single Value

Use Case: Total cart amount

const cart = [
  { item: "Shirt", price: 500 },
  { item: "Shoes", price: 1500 }
];

const total = cart.reduce((sum, item) => sum + item.price, 0);

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✅ 4. find() – Find First Matching Item

Use Case: Get user by email

const users = [
  { id: 1, email: "a@gmail.com" },
  { id: 2, email: "b@gmail.com" }
];

const user = users.find(u => u.email === "b@gmail.com");

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✅ 5. findIndex() – Get Index of Item

Use Case: Remove a user by ID

const idx = users.findIndex(u => u.id === 2);
if (idx !== -1) users.splice(idx, 1);

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✅ 6. some() – Check If Any Item Matches

Use Case: Prevent duplicate email registration

const emails = ["a@gmail.com", "b@gmail.com"];

const alreadyExists = emails.some(email => email === "a@gmail.com");

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✅ 7. every() – Check All Items

Use Case: Validate form fields

const fields = ["name", "email", "password"];
const allFilled = fields.every(field => field.length > 0);

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✅ 8. sort() – Sort Data

Use Case: Sort products by price

const products = [
  { name: "Laptop", price: 50000 },
  { name: "Phone", price: 20000 }
];

products.sort((a, b) => a.price - b.price);

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✅ 9. includes() – Check If Value Exists

Use Case: Show tag as selected

const selectedTags = ["react", "css"];
selectedTags.includes("css"); // true

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✅ 10. forEach() – Loop Through Items

Use Case: Log analytics events

events.forEach(event => sendToAnalytics(event));

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✅ 11. push() – Add Item at End

Use Case: Add new message to chat

messages.push({ text: "Hello!", time: Date.now() });

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✅ 12. pop() – Remove Last Item

Use Case: Undo last drawing action

history.pop();

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✅ 13. unshift() – Add Item at Start

Use Case: Add a notification at top

notifications.unshift({ text: "New like!", read: false });

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✅ 14. shift() – Remove First Item

Use Case: Remove oldest log entry

logs.shift();

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✅ 15. splice() – Insert, Remove, Replace

Use Case: Remove a product from cart

cart.splice(2, 1); // remove item at index 2

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✅ 16. slice() – Copy Part of Array

Use Case: Pagination

const pageData = users.slice(0, 10); // first 10 users

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✅ 17. flat() – Flatten Nested Arrays

Use Case: Merge nested categories

const categories = ["Men", ["Shirts", "Shoes"]];
categories.flat(); // ["Men", "Shirts", "Shoes"]

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🎯 In Short:

These examples cover real-time use cases like: ✔ E-commerce
✔ Authentication
✔ Validation
✔ Filtering lists
✔ UI operations
✔ Pagination
✔ API data transformation
✔ Chat apps
✔ Analytics