Apa bedane antara deklarasi fungsi lan ekspresi fungsi?

Question

IT Interview Practice · Accepted Answer

A **declaration** yaiku pernyataan fungsi sing jeneng; an **expression** assign fungsi menyang variabel. Bedane praktis yaiku **hoisting**.

```js
// Declaration — fully hoisted, callable before its line
declared();             // ✅ works
function declared() { return "hi"; }

// Expression — only the variable binding is hoisted, not the function
expressed();            // ❌ TypeError: expressed is not a function
var expressed = function () { return "hi"; };
```

## Apa sebabe bedane

Function declarations di-hoist **karo tubuh-e**, dadi fungsi lengkap ana sadurunge eksekusi tekan kono. A function expression mung nilai sing di-assign menyang variabel — ing titik early call, `expressed` isih `undefined` (karo `var`) utawa ing TDZ (karo `let`/`const`).

## Kapan nggunakake mana

```js
// expression — for callbacks, conditional definitions, arrow functions
const handler = () => doThing();
const fn = condition ? a : b;
arr.map(x => x * 2);

// declaration — clear, hoisted top-level functions
function calculateTotal(items) { ... }
```

Declarations maca apik kanggo fungsi jeneng top-level lan benefited saka hoisting (sampeyan bisa defile satalikane saka pamakae-e). Expressions kudu kanggo arrow functions, callbacks, IIFEs, lan assign fungsi kanthi kondisional. Arrow functions tansah expressions.

Apa sebabe bedane

Kapan nggunakake mana

Pitakon sing gegandhengan