String.padStart() Pad at the start
Last updated: 2026-09-09
String.padStart() Pad at the start
padStart pads the start to a target length — the classic zero-padding trick.
| Category | Strings |
|---|---|
| ES version | ES2017 |
📝 Syntax
const padded = str.padStart(targetLength, padString);⚙️ Parameters
| targetLength | Target total length including original characters. |
|---|---|
| padString | Optional. Pad string, default is a space. |
Returns：The padded new string.
Mutates the original：No (returns a new value)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
05
00123
09:05:03💡 Tip padStart returns the string unchanged if it already meets the target length.
ℹ️ info A long padString is truncated to fit.
🌐 Browser support
| Browser |  Chrome |
 Edge |
 Firefox |
 Safari |
 Opera |
|---|---|---|---|---|---|
| String.padStart() | ✓ v57 | ✓ v15 | ✓ v48 | ✓ v10 | ✓ v44 |
| Supported by all modern browsers | |||||
🏷️ Related Items
💡 Related Cases
More case studies coming soon — check back later.
📚 Related Tutorials
❓ FAQ
QpadStart vs padEnd?
ApadStart pads the start; padEnd pads the end.
QDefault pad character?
ADefault is a space — pass 0 explicitly.
QWhat if already long enough?
AReturned as-is, no truncation.
