Pattern Breakdown
Understanding the regex pattern ^-?[0-9]*\.?[0-9]+$:
- ^ - Start of string
- $ - End of string
- ? - Optional (zero or one)
- + - One or more
- * - Zero or more
- [...] - Character class
Examples
| Input | Result | Explanation |
|---|---|---|
123.456 |
✓ Match | Positive decimal |
-0.5 |
✓ Match | Negative decimal |
.5 |
✓ Match | No leading zero |
Code Examples
JavaScript
JavaScript
const pattern = /^-?[0-9]*\.?[0-9]+$/;
const text = "123.456";
// Test if string matches
if (pattern.test(text)) {
console.log("Valid!");
}
// Extract matches
const matches = text.match(pattern);
console.log(matches);
Python
Python
import re
pattern = r'^-?[0-9]*\.?[0-9]+$'
text = "123.456"
# Test if string matches
if re.match(pattern, text):
print("Valid!")
# Find all matches
matches = re.findall(pattern, text)
print(matches)
PHP
PHP
<?php
$pattern = '/^-?[0-9]*\.?[0-9]+$/';
$text = "123.456";
// Test if string matches
if (preg_match($pattern, $text)) {
echo "Valid!";
}
// Find all matches
preg_match_all($pattern, $text, $matches);
print_r($matches);
?>
Java
Java
import java.util.regex.*;
String pattern = "^-?[0-9]*\\.?[0-9]+$";
String text = "123.456";
Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(text);
if (m.matches()) {
System.out.println("Valid!");
}
Use Cases
Common applications: Scientific data, financial calculations
- Form validation and input sanitization
- Data extraction and parsing
- Search and replace operations
- API request/response validation
- Log file analysis
Frequently Asked Questions
What is the regex pattern for decimal number regex?
The regex pattern is: ^-?[0-9]*\.?[0-9]+$. Match decimal numbers with optional negative sign and decimal point.
How do I use the decimal number regex pattern in JavaScript?
In JavaScript: const regex = new RegExp('^-?[0-9]*\\.?[0-9]+$'); or const regex = /^-?[0-9]*\.?[0-9]+$/;
Does this pattern work in Python?
Yes, use: import re; pattern = re.compile(r'^-?[0-9]*\.?[0-9]+$') in Python. Most regex patterns are cross-language compatible.
What are common use cases for decimal number regex?
Scientific data, financial calculations
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