Text Processingflags: g

JSON Number (Strict)

Match JSON-spec numbers — disallows leading zeros (no `01`), allows decimals and exponents.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("-?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][-+]?\\d+)?", "g");
const input = "values: 0, 42, -3.14, 6.022e23";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][-+]?\d+)?")
input_text = "values: 0, 42, -3.14, 6.022e23"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][-+]?\d+)?`)
	input := `values: 0, 42, -3.14, 6.022e23`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.

Pattern

regexengine-agnostic

-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][-+]?\d+)?   (flags: g)

Raw source: -?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][-+]?\d+)?

How it works

-? optional sign. (?:0|[1-9]\d*) the integer part: either a single zero or a non-zero digit followed by any digits (no leading zeros allowed per RFC 8259). (?:\.\d+)? optional decimal part. (?:[eE][-+]?\d+)? optional exponent. Strict per JSON spec — won't match `01` or `1.` (which are valid JS but not JSON).