Strings, Template Literals, and String Methods

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Strings in JavaScript

Strings are immutable sequences of UTF-16 code units. You can use single quotes, double quotes, or backtick template literals. Always be consistent — at CPCODELAB we recommend double quotes for source files.

Template Literals

Template literals (backtick strings) support expression interpolation with ${} and can span multiple lines without escape sequences.

javascript

const first = "Alice";
const last = "Smith";
const greeting = `Hello, ${first} ${last}!`;
// "Hello, Alice Smith!"

const multiline = `Line one
Line two
Line three`;

Common String Methods

javascript

const str = "  Hello, World!  ";

str.trim();                    // "Hello, World!"
str.trimStart();               // "Hello, World!  "
str.trimEnd();                 // "  Hello, World!"
str.toLowerCase();             // "  hello, world!  "
str.toUpperCase();             // "  HELLO, WORLD!  "

const clean = str.trim();
clean.includes("World");       // true
clean.startsWith("Hello");     // true
clean.endsWith("!");           // true
clean.indexOf("o");            // 4
clean.lastIndexOf("o");        // 8
clean.slice(7, 12);            // "World"
clean.replace("World", "JS"); // "Hello, JS!"
clean.replaceAll("l", "L");   // "HeLLo, WorLd!"
clean.split(", ");             // ["Hello", "World!"]
"ha".repeat(3);               // "hahaha"
"5".padStart(3, "0");         // "005"

Strings are zero-indexed. str[0] gives the first character. str.length gives the number of UTF-16 code units, which can differ from the number of visible characters for emoji and some Unicode symbols.

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