JavaScript 2025 cheatsheet

JavaScript 2025: Strings

9 common JavaScript 2025 tasks.

Insert values into a string

Use backticks and ${} to build strings, including multi-line ones.

const message = `Hello, ${user.name}! You have ${count} new messages.`;

Turn a string into an array, and back again.

const words = "a,b,c".split(",");
const line = words.join(" | ");

Replace all matches, not just the first.

const clean = text.replaceAll("-", " ");

Pad on the left, for example to make 7 into 07.

const hour = String(7).padStart(2, "0");

Test a string without a regular expression.

url.startsWith("https://");
file.endsWith(".png");
text.includes("error");

Uppercase the first letter and keep the rest.

const title = word[0].toUpperCase() + word.slice(1);

Sort strings using the language's rules, including accents and capitals.

names.sort((a, b) => a.localeCompare(b));

Format with the user's locale conventions.

new Intl.NumberFormat("en-US", { style: "currency", currency: "USD" }).format(1234.5);

Format a date for a locale.

new Intl.DateTimeFormat("en-GB", { dateStyle: "medium" }).format(new Date());