🗺️ JavaScript Map & 🔝 Higher-Order Functions

JavaScript gives us powerful tools to handle data structures and perform array transformations in a clean way.
Today, let’s explore:

✅ Map Object
✅ Higher-Order Functions (map, filter)

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🗺️ 1. The Map Object

🔑 The Map object stores key–value pairs, just like an object, BUT with a twist:

• Keys can be of any data type (string, number, object, etc.)

• Maintains the insertion order

✨ Creating a Map

let mymap = new Map();

// Add data (key → value)
mymap.set("name", "Suraj");
mymap.set("age", 22);
mymap.set("22", "Hardy");  // key is string
mymap.set(22, "Sumit");    // key is number

🔍 Accessing Data

console.log(mymap.get("22")); // Hardy
console.log(mymap.get(22));   // Sumit
console.log(mymap.get("name")); // Suraj

⚡ Notice: "22" (string) and 22 (number) are different keys.

❌ Deleting Data

mymap.delete(22);
mymap.delete("22");
mymap.delete("name");

console.log(mymap);

🔁 Iterating Over Map

for (let [key, value] of mymap) {
    console.log(key, value);
}

🔝 2. Higher-Order Functions

📌 A higher-order function is a function that:
1️⃣ Takes another function as input, OR
2️⃣ Returns a new function

function newfunction() {
    console.log("I am new function");
}

function highOrderFunction(funct) {
    funct(); // call the function
}

highOrderFunction(newfunction);
// Output: I am new function

🔄 3. Useful Higher-Order Functions

🔹 map() → Transform values in an array

const arr = [5, 45, 2, 6];

// Double each element
const result = arr.map((x) => 2 * x);
console.log(result); 
// output
//[10, 90, 4, 12]

🔹 filter() → Extract values that match a condition

const arr = [5, 45, 2, 6];

// Keep only values > 2
const result = arr.filter((x) => x > 2);

console.log(result); 
// [5, 45, 6]

:

👉 Callback Function → A function passed into another function to be run after the first one finishes.

function greet(name , callback)
{
    console.log("Hello " + name);
    callback();
}


function greetings()
{
    console.log("good morning");
}

greet("Suraj" ,greetings )
// output
//Hello suraj
//good morning

(you can copy the code and check the output on given links :→ https://www.programiz.com/javascript/online-compiler/
)

🎯 Wrap-Up

• 🗺️ Map object → stores key–value pairs, supports any data type as key

• 🔝 Higher-order functions → take/return functions

• 🔄 map() → transforms arrays

• 🔍 filter() → extracts based on condition

• Callback()→ call function inside function