Array.findIndex() Find the first matching index
Last updated: 2026-09-09
Array.findIndex() Find the first matching index
findIndex returns the index of the first element satisfying the test, or -1. Commonly paired with splice to replace or remove elements.
| Category | Arrays |
|---|---|
| ES version | ES6 (2015) |
📝 Syntax
const index = array.findIndex((element, index, array) => condition);⚙️ Parameters
| callback | Test function, same semantics as find. |
|---|
Returns：Index of the first match, or -1.
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
1
[ 'weekly report', 'product review', 'code review' ]
-1💡 Tip findIndex stops at the first match, same as find.
💡 Tip Classic combo: findIndex + splice for precise removal.
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| Array.findIndex() | ✓ v45 | ✓ v12 | ✓ v25 | ✓ v8 | ✓ v32 |
| Supported by all modern browsers | |||||
🏷️ Related Array Methods
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
QfindIndex vs indexOf?
AindexOf matches a fixed value strictly; findIndex matches any condition via a callback.
QWhat does -1 mean?
ANothing matched. Always check !== -1 before using the index.
QHow to remove the found element?
Aconst i = arr.findIndex(x => x.id === 3); if (i !== -1) arr.splice(i, 1);
