Basics

Strings

Text values with rich built-in methods and template literals.

1. Explanation

Strings are sequences of characters. Use single, double or backtick quotes. Backticks enable template literals — multiline strings and ${expression} interpolation. Useful methods: length, toUpperCase, toLowerCase, includes, indexOf, slice, split, replace, trim, repeat.

2. Example

Try it yourself

const name = "javascript";
console.log(name.length);              // 10
console.log(name.toUpperCase());       // JAVASCRIPT
console.log(name.includes("script"));  // true
console.log(name.slice(0, 4));         // java
console.log("a,b,c".split(","));       // ["a","b","c"]

const age = 22;
console.log(`I am ${age} years old`); // template literal

Console

Click Run to see output.

3. Expected output

output

10
JAVASCRIPT
true
java
["a","b","c"]
I am 22 years old

4. Common mistakes

✗Trying to mutate a string (s[0] = 'A') — strings are immutable
✗Using + for complex concatenation instead of template literals
✗Forgetting that .replace replaces only the first match without /g flag

5. Practice questions

Reverse a string
Count how many times the letter 'a' appears in a sentence
Capitalize the first letter of each word

→ Try more practice problems