Functions : Declaration, Expression, IIFE, Callback and More
Functions are fundamental building blocks in Node.js, used to organize code and handle logic.
1. Function Declaration
function greet(name) {
return `Hello, ${name}!`;
}
2. Function Expression
const greet = function(name) {
return `Hello, ${name}!`;
};
3. Arrow Function
const greet = (name) => `Hello, ${name}!`;
4. Immediately Invoked Function Expression (IIFE)
(function() {
console.log('IIFE runs immediately!');
})();
5. Callback Functions
Functions passed as arguments.
function fetchData(callback) {
// Simulate async operation
setTimeout(() => {
callback('Data received');
}, 1000);
}
fetchData((data) => console.log(data));
6. Anonymous Functions
Functions without a name, often used as callbacks.
setTimeout(function() {
console.log('Anonymous function');
}, 1000);
7. Rest Parameters
Collects all remaining arguments into an array.
function sum(...numbers) {
return numbers.reduce((acc, num) => acc + num, 0);
}
8. Default Parameters
Setting default values for function parameters.
function greet(name = 'Guest') {
return `Hello, ${name}!`;
}
9. Higher-Order Functions
Functions that accept or return other functions.
function createMultiplier(multiplier) {
return (x) => x * multiplier;
}
const double = createMultiplier(2);
10. Async/Await
async function fetchData() {
const data = await fetch('url');
console.log(data);
}
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