The following are the JavaScript supported features. They can be classified into General, String methods, Object methods, and Array methods:

General:

• Boolean values, numbers, strings, objects, arrays, functions, and regular expressions
• ES5.1 operators, ES7 exponentiation operators
• ES5.1 statements are var, if, else, switch, for, for in, while, do while, break, continue, return, try, catch, throw, and finally
• ES6 number and math properties and methods
• ES5.1 function methods are call, apply, and bind
• ES5.1 RegExp methods are test, and exec
• ES5.1 Date methods
• ES5.1 JSON objects
• ES5.1 global functions are isFinite, isNaN, parseFloat, parseInt, decodeURI, decodeURIComponent, encodeURI, and encodeURIComponent
• Error objects are Error, EvalError, InternalError, RangeError, ReferenceError, SyntaxError, TypeError, and URIError
• File system methods (Node.js-style) are fs.readFile, fs.readFileSync, fs.appendFile, fs.appendFileSync, fs.writeFile, and fs.writeFileSync

String methods:

• ES5.1: fromCharCode, concat, slice, substring, substr, charAt, charCodeAt, indexOf, lastIndexOf, toLowerCase, toUpperCase, trim, search, match, split, and replace
• ES6: fromCodePoint, codePointAt, includes, startsWith, endsWith, and repeat non-standard: fromUTF8, toUTF8, fromBytes, and toBytes

Object methods:

• ES5.1: create (support without properties list), keys, defineProperty, defineProperties, getOwnPropertyDescriptor, getPrototypeOf, hasOwnProperty, isPrototypeOf, preventExtensions, isExtensible, freeze, isFrozen, seal, isSealed

Array methods:

• ES5.1: isArray, slice, splice, push, pop, unshift, shift, reverse, sort, join, concat, indexOf, lastIndexOf, forEach, some, every, filter, map, reduce, reduceRight
• ES6: of, fill, find, findIndex
• ES7: includes