Array.includes() Check whether an item exists
Last updated: 2026-09-09
Array.includes() Check whether an item exists
includes reports whether the array contains a value, returning true or false. Clearer than indexOf !== -1 and NaN-aware.
| Category | Arrays |
|---|---|
| ES version | ES2016 (2016) |
📝 Syntax
array.includes(searchValue, fromIndex);⚙️ Parameters
| searchValue | The value to find, using SameValueZero (like strict equality but NaN equals NaN). |
|---|---|
| fromIndex | Optional. Start position; negative counts from the end. |
Returns：A boolean.
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
true
-1
false💡 Tip includes is the preferred existence check — shorter than indexOf !== -1 and NaN-aware.
ℹ️ info SameValueZero: +0 equals -0 and NaN equals NaN; the only difference from Object.is is +0/-0.
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| Array.includes() | ✓ v47 | ✓ v14 | ✓ v43 | ✓ v9 | ✓ v34 |
| Supported by all modern browsers | |||||
🏷️ Related Array Methods
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
Qincludes or indexOf?
AUse includes for existence; indexOf only when you need the position.
QDoes includes find objects?
AOnly by reference. Use some(u => u.id === 3) to match objects by property.
QWhat is fromIndex for?
AIt starts the search later; negatives count from the end — e.g. checking only the last 3 items.
