Lookbehind (Positive) Regex Pattern

Live Regex Tester

Pattern Breakdown

Code Examples

const regex = /(?<=\$)\d+(\.\d{2})?/g;
const test = "Price: $49.99";
console.log(regex.test(test)); // true

// Extract matches
const matches = test.match(regex);
console.log(matches);

import re

pattern = r'(?<=\$)\d+(\.\d{2})?'
test = "Price: $49.99"
match = re.findall(pattern, test)
print(match)  # Found!

package main

import (
    "fmt"
    "regexp"
)

func main() {
    re := regexp.MustCompile(`(?<=\$)\d+(\.\d{2})?`)
    fmt.Println(re.MatchString("Price: $49.99")) // true
}

Common Use Cases

Match Examples

About the Lookbehind (Positive) Regex

Demonstrates positive lookbehind: matches numbers only when preceded by $. Extracts prices without the dollar sign.

Regular expressions (regex) are powerful pattern matching tools used across virtually all programming languages. The lookbehind (positive) pattern is classified as advanced difficulty in the advanced patterns category. This pattern is specifically designed for JavaScript.

When using this regex, always consider edge cases and test thoroughly with real-world data. Use the interactive tester above to validate the pattern against your specific inputs before deploying to production.

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