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What is it?

Tiny package for detecting reserved words.

Reserved Word is either a Keyword, or a Future Reserved Word, or a Null Literal, or a Boolean Literal. See: ES5 #7.6.1 and ES6 #11.6.2.


npm install reserved-words


check(word, [dialect], [strict])

Returns true if provided identifier string is a Reserved Word in some ECMAScript dialect (ECMA-262 edition).

If the strict flag is truthy, this function additionally checks whether word is a Keyword or Future Reserved Word under strict mode.


var reserved = require('reserved-words');
reserved.check('volatile', 'es3'); // true
reserved.check('volatile', 'es2015'); // false
reserved.check('yield', 3); // false
reserved.check('yield', 6); // true


es3 (or 3)

Represents ECMA-262 3rd edition.

See section 7.5.1.

es5 (or 5)

Represents ECMA-262 5th edition (ECMAScript 5.1).

Reserved Words are formally defined in ECMA262 sections and

es2015 (or es6, 6)

Represents ECMA-262 6th edition.

Reserved Words are formally defined in sections and


Licensed under The MIT License