parseInt() Parse an integer
Last updated: 2026-09-09
parseInt() Parse an integer
parseInt parses a string and returns an integer, ignoring leading whitespace.
| Category | Global Functions |
|---|---|
| ES version | ES1 |
📝 Syntax
parseInt(string, radix);⚙️ Parameters
| string | The string to parse. |
|---|---|
| radix | Optional. Base 2~36 — always specify. |
Returns：The parsed integer, or NaN.
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
42
42
3
26
NaN⚠️ Warning parseInt without radix is unreliable — ALWAYS specify parseInt(str, 10).
💡 Tip parseInt truncates decimals — use parseFloat for floats.
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| parseInt() | ✓ 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
QparseInt vs parseFloat?
AparseInt parses integers (truncates decimals); parseFloat parses floats.
QWhy always specify radix?
AWithout radix '010' may parse as 8 (octal) — unpredictable behavior.
QparseInt('abc')?
AReturns NaN — the first character is not a digit.
