Web Development - HTML, CSS &… on Telegram: “const fileName = "report.pdf"; console.log(fileN…”

const fileName = "report.pdf";
console.log(fileName.endsWith(".pdf")); // true

🔹 Finding Positions

1️⃣3️⃣ indexOf()

Returns the position of the first occurrence.

const message = "Hello JavaScript";
console.log(message.indexOf("JavaScript")); // 6
console.log(message.indexOf("Python")); // -1 - not found

1️⃣4️⃣ lastIndexOf()

Returns the position of the last occurrence.

const text = "JavaScript is powerful. JavaScript is popular.";
console.log(text.lastIndexOf("JavaScript")); // 25

🔹 Extracting Parts of a String

1️⃣5️⃣ slice()

slice() extracts part of a string.

const language = "JavaScript";
console.log(language.slice(0, 4)); // Java

The ending index is not included.

• 0 → J

• 1 → a

• 2 → v

• 3 → a

• 4 → S

• So slice(0, 4) returns characters from index 0 through 3.

1️⃣6️⃣ Negative Indexes

You can use negative indexes with slice().

const language = "JavaScript";
console.log(language.slice(-6)); // Script

🔹 substring()

1️⃣7️⃣ substring()

substring() can also extract part of a string.

const language = "JavaScript";
console.log(language.substring(0, 4)); // Java

For modern JavaScript code, slice() is often more convenient because it supports negative indexes.

🔹 Replacing Text

1️⃣8️⃣ replace()

Replaces the first matching occurrence.

const message = "I like JavaScript";
const updated = message.replace("JavaScript", "Python");

console.log(updated); // I like Python

1️⃣9️⃣ replaceAll()

Replaces all matching occurrences.

const message = "JavaScript is great. JavaScript is popular.";
const updated = message.replaceAll("JavaScript", "JS");
console.log(updated); // JS is great. JS is popular.

🔹 Splitting Strings

2️⃣0️⃣ split()

split() converts a string into an array.

const names = "Amit,Priya,Rahul";
const result = names.split(",");
console.log(result); // ["Amit", "Priya", "Rahul"]

const sentence = "Learn JavaScript step by step";
const words = sentence.split(" ");
console.log(words); // ["Learn", "JavaScript", "step", "by", "step"]

🔹 Joining Data

2️⃣1️⃣ join()

join() combines array elements into a string.

const words = ["Learn", "JavaScript"];
const sentence = words.join(" ");
console.log(sentence); // Learn JavaScript

Notice:

• split() → string → array

• join() → array → string

⭐ Template Literals

2️⃣2️⃣ What Are Template Literals?

Template literals use backticks:

const message = `Hello`;

Their biggest advantage is easy string interpolation.

const name = "Rahul";
const age = 25;
const message = `My name is ${name} and I am ${age} years old.`;

console.log(message); // My name is Rahul and I am 25 years old.

2️⃣3️⃣ Expressions Inside Template Literals

You can also use expressions.

const price = 1000;
const quantity = 3;
const total = `Total: ${price * quantity}`;
console.log(total); // Total: 3000

2️⃣4️⃣ Multi-line Strings

Template literals make multi-line text easier.

const message = `
Hello Rahul,

Welcome to JavaScript.

Keep learning!
`;
console.log(message);