JavaScript String Methods: A Complete Reference

Method	Description	Example
length	Returns the length of the string	let str = "whereisstuff"; str.length // output 12
charAt	Returns the character index of the string	let str = "hello"; str[0] // output "h" str.charAt(0) // output "h"
toUpperCase	Returns the uppercase string	let str = "Hello"; str.toUpperCase(); // output "HELLO"
toLowerCase	Returns the lowercase string	let str = "WORLD"; str.toLowerCase(); // output "world"
indexOf	Returns the index of the first occurrence	let str = "JavaScript is fun"; str.indexOf("is"); // 11
includes	Checks if the substring exists	let str = "JavaScript is fun"; str.includes("fun"); // true str.includes("bun"); // false
startsWith	Checks the start of string	let str = "JavaScript is fun"; str.startsWith("Java"); // true str.startsWith("fun"); // false
endsWith	Checks the end of string	let str = "JavaScript is fun"; str.endsWith("Java"); // false str.endsWith("fun"); // true
slice(start, end)	slice string	let str = "JavaScript is fun"; str.slice(0, 4); // "Java"
concat	Joins two or more strings	let str = "JavaScript"; str.concat(" is fun"); // "JavaScript is fun"
trim	Removes whitespace	let str = " JavaScript "; str.trim(); // "JavaScript"
replace	Replaces a substring	let str = "JavaScript"; str.replace("Java", "Hello"); // "HelloScript"
split	Splits a string into an array	let str = "Java Script"; str.split(" "); // ["Java","Script"]
repeat	Repeats a string	let str = "Hi"; str.repeat(3); //HiHiHi
padStart / padEnd	Pads a string	let str = "5"; str.padStart(3, "0") // "0005" str.padEnd(3, "0") // "5000"
Number	Convert string to a number	let str = "5"; Number(str) // 5
parseInt	Convert string to a number	let str = "5"; Number(str) // 5 let str2 = "20px"; Number(str2) // 20
parseFloat	Convert string to a float number	let str = "123.45"; parseFloat(str) // 123.45

length:

Returns the length of the string

Example

let str = "whereisstuff";

str.length // output 12

Try it yourself

Access Characters:

Returns the character index of the string

Example

let str = "Hello";

console.log(str[0]); // H

console.log(str.charAt(1)); // e

Try it yourself

Change Case:

toUppercase() → Returns the uppercase string

toLowercase() → Returns the Lowercase string

Example

console.log("Hello".toUpperCase()); // HELLO

console.log("WORLD".toLowerCase()); // world

Try it yourself

Searching Strings:

indexOf() → Returns the index of the first occurrence
includes() → Checks if the substring exists
startsWith() / endsWith() → Checks the start/end

Example

let str = "JavaScript is fun";

console.log(str.indexOf("is")); // 11

console.log(str.includes("fun")); // true

console.log(str.startsWith("Java")); // true

console.log(str.endsWith("fun")); // true

Try it yourself

Extracting Parts of a String:

slice(start, end)
substring(start, end)

Example

let str = "JavaScript";

console.log(str.slice(0, 4)); // Java

console.log(str.substring(0, 4)); // Java

Try it yourself

String Manipulation:

concat() → Joins two or more strings
trim() → Removes whitespace
replace() → Replaces a substring
split() → Splits a string into an array

Example

let str = " Hello World ";

console.log(str.trim()); // "Hello World"

console.log(str.replace("World", "JavaScript")); // " Hello JavaScript "

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

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Repeat and Pad:

repeat() → Repeats a string
padStart() / padEnd() → Pads a string

Example

console.log("Hi".repeat(3)); // HiHiHi

console.log("5".padStart(3, "0")); // 005

console.log("5".padEnd(3, "0")); // 500

Try it yourself

String to Number Conversion

Number() → Convert string to a number
parseInt() / parseFloat()

Example

let str = "123";

console.log(Number(str)); // 123

console.log(parseInt(str)); // 123

console.log(parseFloat("123.45")); // 123.45

Try it yourself

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Method

Description

Example

length:

Access Characters:

Change Case:

Searching Strings:

Extracting Parts of a String:

String Manipulation:

Repeat and Pad:

String to Number Conversion