Strings

Text in TypeScript is the string primitive: an immutable sequence of characters with the same rich method set as JavaScript. One type note up front: always write lowercase string in annotations. The capitalized String is the legacy wrapper object — almost never what you want.

Three quoting styles

const single = 'hello';
const double = "hello";
const tick = `hello`;

Single and double quotes are interchangeable — pick one and be consistent. Backticks create template literals, which have two superpowers: interpolation and multi-line text.

const name: string = "Alice";
const age: number = 30;
console.log(`${name} is ${age} years old`); // Alice is 30 years old

Anything inside the braces is a real expression, and TypeScript type-checks it like any other code.

The everyday methods

const s: string = "hello, world";

s.length;                 // 12 — a property, not a method (no parentheses)
s.toUpperCase();          // "HELLO, WORLD"
s.includes("world");      // true
s.slice(0, 5);            // "hello"
s.split(", ");            // ["hello", "world"]
s.replace("world", "TS"); // "hello, TS"
s[0];                     // "h" — indexing works

The trap: strings are immutable

No string method ever changes the string in place — every method returns a NEW string:

let s = "hello";
s.toUpperCase();
console.log(s);      // still "hello" — the result was thrown away!

s = s.toUpperCase();
console.log(s);      // "HELLO" — you must keep the return value

There is also no s.reverse() — arrays can reverse themselves, strings cannot.

The reverse idiom

Since a string cannot reverse itself, hop through an array and back:

const reversed = s.split('').reverse().join('');

Step by step:

• split('') explodes the string into an array of one-character strings (string[]).
• reverse() reverses that array in place.
• join('') glues the characters back together with no separator.

(A caveat for later: split('') cuts along UTF-16 code units, so emoji and some non-Latin characters get mangled. For plain ASCII text — like this exercise — it is exactly right.)

Your exercise

The starter reads one full line from stdin:

const word: string = require('fs').readFileSync(0, 'utf-8').trim();

Print that line reversed, using the split/reverse/join idiom.

Watch out for the hidden test: the input line can contain a space — hello world must become dlrow olleh. The exact mistake the grader will catch is reversing the words instead of the characters: splitting on ' ' and reversing gives world hello, which fails. Reverse every character of the entire line, spaces included, and print only the result.