Functions

Declaration, parameters, return values, and arrow functions

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Function Declarations vs Arrow Functions

Greet (declaration)

Sum (arrow)

// Declaration function greet(name) { return `Hello, ${name}!`; } // Arrow function const sum = (a, b) => a + b;

Default Params, Rest/Spread

Default Params

Rest/Spread

function welcome(name = 'Developer') { return `Welcome, ${name}!`; } function maxOf(...nums) { // rest return Math.max(...nums); // spread }

Full Code Used in This Demo

HTML

<button onclick="runGreet()">Run</button>
<div id="out-greet"></div>
<button onclick="runSum()">Run</button>
<div id="out-sum"></div>
<button onclick="runDefaultParams()">Run</button>
<div id="out-default"></div>
<button onclick="runRestSpread()">Run</button>
<div id="out-rest"></div>

CSS

.btn { background: #3b82f6; color: #fff; border-radius: 8px; }

JavaScript

function greet(name) { return `Hello, ${name}!`; }
const sum = (a, b) => a + b;
function welcome(name = 'Developer') { return `Welcome, ${name}!`; }
function maxOf(...nums) { return Math.max(...nums); }