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What is this?

This is intended to be a fun way of accepting alternatives to false or "no" in CLI prompts, web forms, etc. For example, you might want to allow users to define nil or nope to disable something.

Usage

const falsey = require('{%= name %}');

console.log(falsey());       //=> true
console.log(falsey(false));  //=> true
console.log(falsey('nil'));  //=> true
console.log(falsey('nope')); //=> true
console.log(falsey('yes'));  //=> false

Examples

Any value that is not falsey (according to JavaScript) and is not in the list of falsey keywords will return false:

falsey('abc');
falsey(true);
falsey(1);
falsey('1');
falsey({});
falsey([]);

Any value that is falsey (according to JavaScript) or is in the list of falsey keywords will return true:

falsey();          //=> true
falsey('');        //=> true
falsey(0);         //=> true
falsey(false);     //=> true
falsey(NaN);       //=> true
falsey(null);      //=> true
falsey(undefined); //=> true
falsey(void 0);    //=> true

Falsey keywords

If a value matches one of the built-in "falsey" keywords (all strings) it will return true:

  • 0
  • false
  • nada
  • nil
  • nay
  • nah
  • negative
  • no
  • none
  • nope
  • nul
  • null
  • nix
  • nyet
  • uh-uh
  • veto
  • zero

Customize falsey keywords

Pass an array of custom keywords that should return true when evaluated as falsey:

falsey('zilch', ['no', 'nope', 'nada', 'zilch']); //=> true

Disable built-in keywords by passing an empty array:

falsey('nil', []); //=> false

Extend built-in keywords

Built-in keywords are exposed on the .keywords property so that you may extend them with your own keywords:

falsey('zilch', falsey.keywords.concat(['zilch'])); //=> true

Release history

v1.0

Breaking changes

  • objects will now always returns false
  • more words were added to the built-in list of falsey keywords