Learning Java Script:Null,Undefined and Template Literals.

In JavaScript, null is a primitive value that represents the intentional absence of any object value. It is often used to indicate that a variable should hold an object but currently does not.

Key Points about null in JavaScript:

1. Type

   typeof null; // "object"

• This is a well-known quirk in JavaScript. Although null is a primitive, typeof null returns "object". This is due to a bug in the original version of JavaScript and is kept for compatibility.

1. Assignment

   let user = null;

• This indicates that user is intentionally set to have no value, perhaps until a valid object is assigned later.

1. Comparison with undefined

   null == undefined; // true
   null === undefined; // false

• == does type coercion, so it considers them equal.
• === is strict comparison, so they are not equal because their types differ (null is object, undefined is undefined).

1. Use Cases

• Resetting a variable
• Representing missing data
• Checking the result of DOM operations (e.g., document.getElementById("nonexistent") returns null)

In JavaScript, undefined is a primitive value that means a variable has been declared but not yet assigned a value.

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🔹 What is undefined?

undefined is automatically assigned to variables that have been declared but not initialized.

let x;
console.log(x); // undefined

It also appears in other situations when a value is missing or not provided.

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🔸 Common Cases When undefined Appears

1. Uninitialized Variables

let name;
console.log(name); // undefined

2. Missing Function Return

If a function does not explicitly return a value:

function sayHi() {
  console.log("Hi!");
}
let result = sayHi();  // Logs "Hi!"
console.log(result);   // undefined

3. Missing Function Arguments

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

🔷 Template Literals in JavaScript (ES6)

Template literals (also called template strings) are a cleaner, more powerful way to create strings in JavaScript. They were introduced in ES6 (ECMAScript 2015) and are enclosed by backticks (`) instead of single (') or double (") quotes.

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✅ Key Features of Template Literals

1. Multi-line Strings

const poem = `Roses are red,
Violets are blue,
JavaScript is awesome,
And so are you.`;

console.log(poem);

No need for \n or string concatenation.

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2. String Interpolation (Variable/Expression Insertion)

Use ${} to insert variables or expressions directly inside the string.

const name = "Alice";
const age = 25;

const greeting = `Hello, my name is ${name} and I am ${age} years old.`;
console.log(greeting);

You can even put expressions inside:

const a = 5;
const b = 10;

console.log(`The sum of ${a} and ${b} is ${a + b}.`);

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3. Function Calls Inside ${}

function getTime() {
  return new Date().toLocaleTimeString();
}

console.log(`The current time is: ${getTime()}`);

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