JavaScript version
isOctal.js
const isOctal = (str) => /^(0o)?[0-7]+$/i.test(str);TypeScript version
isOctal.ts
const isOctal = (str: string): boolean => /^(0o)?[0-7]+$/i.test(str);const isOctal = (str) => /^(0o)?[0-7]+$/i.test(str);const isOctal = (str: string): boolean => /^(0o)?[0-7]+$/i.test(str);