String Methods in JavaScript

The String object provides a variety of methods for working with texts. Let’s take a look at some of the most useful ones.

Manipulation Methods

concat()

Combines two or more strings and returns a new string.

const str1 = "Hello";
const str2 = "World";
const result = str1.concat(" ", str2);

console.log(result); // "Hello World"

slice()

Extracts a section of a string and returns a new string without modifying the original.

const str = "JavaScript";
const result = str.slice(0, 4);

console.log(result); // "Java"

substring()

Returns a part of the string between the specified indices.

const str = "JavaScript";
const result = str.substring(4, 10);

console.log(result); // "Script"

substr()

Similar to substring(), but the second parameter specifies the length of the substring.

const str = "JavaScript";
const result = str.substr(4, 6);

console.log(result); // "Script"

split()

Splits the string into an array of substrings using a specified delimiter.

const str = "Hello World";
const result = str.split(" ");

console.log(result); // ["Hello", "World"]

replace()

Replaces a part of the string with another string or regular expression.

const str = "Hello World";
const result = str.replace("World", "JavaScript");

console.log(result); // "Hello JavaScript"

toUpperCase()

Converts all characters in the string to uppercase.

const str = "Hello World";
const result = str.toUpperCase();

console.log(result); // "HELLO WORLD"

toLowerCase()

Converts all characters in the string to lowercase.

const str = "Hello World";
const result = str.toLowerCase();

console.log(result); // "hello world"

trim()

Removes whitespace from both ends of the string.

const str = "   Hello World   ";
const result = str.trim();

console.log(result); // "Hello World"

Search Methods

indexOf()

Returns the index of the first occurrence of a substring, or -1 if not found.

const str = "Hello World";
const index = str.indexOf("World");

console.log(index); // 6

lastIndexOf()

Returns the index of the last occurrence of a substring, or -1 if not found.

const str = "Hello World World";
const index = str.lastIndexOf("World");

console.log(index); // 12

includes()

Determines if a substring is present within a string, returning true or false.

const str = "Hello World";
const result = str.includes("World");

console.log(result); // true

startsWith()

Determines if a string starts with the characters of a substring, returning true or false.

const str = "Hello World";
const result = str.startsWith("Hello");

console.log(result); // true

endsWith()

Determines if a string ends with the characters of a substring, returning true or false.

const str = "Hello World";
const result = str.endsWith("World");

console.log(result); // true

Comparison Methods

localeCompare()

Compares two strings in a specific locale and returns a number indicating the comparison.

const str1 = "a";
const str2 = "b";
const result = str1.localeCompare(str2);
console.log(result); // -1 (because "a" is less than "b" in lexicographic order)

normalize()

Returns the normalized Unicode form of the string, useful for comparing Unicode characters.

const str = "\u00F1";
const normalizedStr = str.normalize("NFD");
console.log(normalizedStr); // "ñ"

Conversion Methods

toString()

Converts and returns the string as a text representation.

const num = 123;
const str = num.toString();
console.log(str); // "123"

valueOf()

Returns the primitive value of a String object.

const str = new String("Hello World");
const primitiveValue = str.valueOf();
console.log(primitiveValue); // "Hello World"

Access Methods

charAt()

Returns the character at the specified index.

const str = "Hello World";
const char = str.charAt(6);

console.log(char); // "W"

charCodeAt()

Returns the Unicode value of the character at the specified index.

const str = "Hello World";
const code = str.charCodeAt(6);

console.log(code); // 87 (Unicode code for "W")

codePointAt()

Returns the Unicode value of a character at the specified index, including characters over 16 bits.

const str = "😊";
const codePoint = str.codePointAt(0);

console.log(codePoint); // 128522

Template Methods

padStart()

Pads the string at the start with another string until reaching a specified length.

const str = "5";
const paddedStr = str.padStart(3, "0");

console.log(paddedStr); // "005"

padEnd()

Pads the string at the end with another string until reaching a specified length.

const str = "5";
const paddedStr = str.padEnd(3, "0");

console.log(paddedStr); // "500"

repeat()

Returns a new string containing a specified number of copies of the original string concatenated.

const str = "abc";
const repeatedStr = str.repeat(3);

console.log(repeatedStr); // "abcabcabc"

Regex Methods

match()

Searches for matches between a string and a regular expression, returning an array or null.

const str = "Hello World";
const result = str.match(/World/);
console.log(result); // ["World"]

matchAll()

Returns an iterator with all matches of a regular expression in the string.

const str = "Hello World World";
const iterator = str.matchAll(/World/g);
console.log([...iterator]); // [["World"], ["World"]]