The most basic and frequently used methods for strings and numbers in JavaScript.
These methods help you perform common operations with ease.

Basic String Methods

toUpperCase()

Converts a string to uppercase.

const str = "hello";
console.log(str.toUpperCase()); 
// "HELLO"

toLowerCase()

Converts a string to lowercase.

const str = "HELLO";
console.log(str.toLowerCase()); 
// "hello" 

trim()

Removes whitespace from both ends of a string.

const str = "  Hello  ";
console.log(str.trim()); 
// "Hello"

slice(start, end)

Returns a part of a string from start to end (excluding end).

const str = "Hello World";
console.log(str.slice(0, 5)); 
// "Hello"

replace(old, new)

Replaces the first occurrence of the substring old with new.

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

Basic Number Methods

toFixed(digits)

Returns a string representing a number with a fixed number of decimal places.

const num = 3.14159;
console.log(num.toFixed(2)); 
// "3.14"

toString(radix)

Converts a number to a string.

const num = 10;
console.log(num.toString()); 
// "10"

Number()

The Number() function converts a value to a number.

console.log(Number("42")); 
// 42

parseInt()

Parses a string and returns an integer.

console.log(parseInt("42")); 
// 42
console.log(parseInt("42abc")); 
// 42

Unary plus (+)

The unary plus operator converts a value to a number.

console.log(+"42"); 
// 42
console.log(+"42abc"); 
// NaN
console.log(+true); 
// 1
console.log(+false); 
// 0