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JS Functions
A function in JavaScript is a reusable block of code designed to perform a specific task. Functions make code modular, readable, and reusable.
Syntax:
function functionName(parameters) {
// Function body
return value;
}
Function Declaration:
A function declaration defines a named function using the function keyword.
Example
function greet(name) {
return `Hello, ${name}!`;
}
console.log(greet("Alice")); // Output: Hello, Alice!
Function Expression:
A function expression assigns a function to a variable.
Syntax:
const functionName = function(parameters) {
// Function body
return value;
}
Example
let greet = function(name) {
return `Hello, ${name}!`;
}
console.log(greet("Alice")); // Output: Hello, Alice!
Arrow Functions (ES6):
Arrow functions provide a shorter syntax and automatically bind this.
Syntax:
const functionName = (parameters) => {
// Function body
};
Example
const add = (a, b) => {
return a + b;
};
console.log(add(5, 3)); // Output: 8
// Single Parameter: Parentheses can be omitted
const greet = name => `Hello, ${name}`;
console.log(greet('Alice')); // Output: Hello, Alice!
// No Parameters: Use empty parentheses
const sayHi = () => console.log("Hi!");
sayHi();
Immediately Invoked Function Expressions (IIFE):
An IIFE runs immediately after being defined.
Example
(function() {
console.log("I am an IIFE!"); // Output: I am an IIFE!
})();
// Arrow Function IIFE:
(() => {
console.log("IIFE with Arrow Function!"); // Output: IIFE with Arrow Function!
})();