String Methods
JavaScript provides a variety of built-in methods to manipulate and work with strings. These methods make it easier to perform operations like searching, slicing, replacing, and transforming strings. Strings are immutable, so these methods return a new string or value without modifying the original string.
Here are some of the most commonly used string methods in JavaScript:
1. Accessing Characters
charAt(index): Returns the character at a specific index.
charCodeAt(index): Returns the Unicode value of the character at a specific index.
let str = "Hello, World!";
console.log(str.charAt(0)); // "H"
console.log(str.charCodeAt(0)); // 72 (Unicode of 'H')
2. Searching Strings
indexOf(value): Returns the first index of the specified value, or -1 if not found.
lastIndexOf(value): Returns the last index of the specified value.
includes(value): Checks if a string contains a specified value; returns true or false.
startsWith(value): Checks if a string starts with a specific value.
endsWith(value): Checks if a string ends with a specific value.
let str = "Hello, JavaScript!";
console.log(str.indexOf("Java")); // 7
console.log(str.lastIndexOf("o")); // 4
console.log(str.includes("Script")); // true
console.log(str.startsWith("Hello")); // true
console.log(str.endsWith("!")); // true
3. Extracting Parts of Strings
slice(start, end): Extracts a portion of a string and returns it.
substring(start, end): Similar to slice, but cannot accept negative indexes.
substr(start, length): Extracts a substring based on the starting index and length. (Deprecated but still supported)
let str = "JavaScript is fun!";
console.log(str.slice(0, 10)); // "JavaScript"
console.log(str.substring(4, 10)); // "Script"
console.log(str.substr(0, 4)); // "Java"
4. Modifying Strings
toUpperCase(): Converts the string to uppercase.
toLowerCase(): Converts the string to lowercase.
trim(): Removes whitespace from both ends of a string.
trimStart() / trimEnd(): Removes whitespace from the start or end of a string.
let str = " Hello World! ";
console.log(str.toUpperCase()); // " HELLO WORLD! "
console.log(str.toLowerCase()); // " hello world! "
console.log(str.trim()); // "Hello World!"
console.log(str.trimStart()); // "Hello World! "
console.log(str.trimEnd()); // " Hello World!"
5. Replacing Content
replace(value, newValue): Replaces the first occurrence of a value.
replaceAll(value, newValue): Replaces all occurrences of a value.
let str = "I love JavaScript. JavaScript is amazing!";
console.log(str.replace("JavaScript", "JS")); // "I love JS. JavaScript is amazing!"
console.log(str.replaceAll("JavaScript", "JS")); // "I love JS. JS is amazing!"
6. Splitting and Joining Strings
split(delimiter): Splits the string into an array based on a delimiter.
concat(value1, value2, ...): Concatenates two or more strings.
let str = "apple,banana,cherry";
let fruits = str.split(","); // ["apple", "banana", "cherry"]
console.log(fruits);
let str1 = "Hello";
let str2 = "World";
console.log(str1.concat(", ", str2, "!")); // "Hello, World!"