Array.isArray() Is it an array
Last updated: 2026-09-09
Array.isArray() Is it an array
Array.isArray is the standard check — typeof returns object for arrays and instanceof fails across frames.
| Category | Arrays |
|---|---|
| ES version | ES5 (2009) |
📝 Syntax
Array.isArray(value);⚙️ Parameters
| value | Any value to check. |
|---|
Returns：true if the value is an array.
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
true
false
false
1💡 Tip Array.isArray is the only reliable check — instanceof fails across frames.
ℹ️ info Array-likes (arguments, NodeList) are not arrays — convert with [...nodeList] or Array.from().
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| Array.isArray() | ✓ v1 | ✓ v12 | ✓ v1.5 | ✓ v3 | ✓ v10.5 |
| Supported by all modern browsers | |||||
🏷️ Related Array Methods
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
QWhy not instanceof?
Ainstanceof checks the prototype chain and fails across frames; Array.isArray uses an internal brand and is always right.
QDoes it recognize array-likes?
ANo — {length: 3} is false. Convert with Array.from().
QIs it static?
AYes — it lives on the constructor: Array.isArray(x), not arr.isArray().
