function Function declaration
Last updated: 2026-09-09
function Function declaration
function declares a reusable callable. Functions are first-class citizens in JS.
| Category | Statements |
|---|---|
| ES version | ES1 |
📝 Syntax
function fnName(param1, param2) { return result; }Returns：The return value (undefined without return).
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
Hello, Zhang
Hello, Li💡 Tip Function declarations are hoisted — callable before declaration.
ℹ️ info Default parameters: function greet(name = 'Guest').
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| function | ✓ v1 | ✓ v12 | ✓ v1 | ✓ v1 | ✓ v1 |
| Supported by all modern browsers | |||||
🏷️ Related Items
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
QDeclaration vs arrow function?
AKey difference is this binding: declarations have their own this; arrows inherit.
QCan a function return multiple values?
ANot directly — return an array or object and destructure.
QToo many parameters?
AUse object destructuring for 3+ params.
