jonschlinkert/falsey

Like other checkers, returns true if `value` is falsey. Strings, arrays and `arguments` objects with a length of `0`, and objects with no own enumerable properties are considered falsey. Will also check against user-defined "special cases".

falsey

Returns true if the given is falsey (according to JavaScript) or matches a 'falsey' keyword.

Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your ❤️ and support.

Install

Install with npm:

$ npm install --save falsey

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('falsey');

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

About

Contributing

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

Running Tests

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

$ npm install && npm test

Building docs

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

Related projects

You might also be interested in these projects:

• is-number: Returns true if the value is a number. comprehensive tests. | homepage
• is-primitive: Returns true if the value is a primitive. | homepage
• isobject: Returns true if the value is an object and not an array or null. | homepage
• kind-of: Get the native type of a value. | homepage

Contributors

Commits	Contributor
12	jonschlinkert
9	doowb
3	jesstelford

Author

Jon Schlinkert

• LinkedIn Profile
• GitHub Profile
• Twitter Profile

License

Copyright © 2018, Jon Schlinkert. Released under the MIT License.

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This file was generated by verb-generate-readme, v0.6.0, on March 18, 2018.

falsey's Issues

No falsey non empty strings checking

Right know isFalse(' ') returns false, IMHO that's wrong, as falsey might be used for simple data validation, this may be kind of unwated behaviour, opinions?

CLI

Easy way to find if something is falsey through through command line... Exits with error when not falsey.

undefined string as falsey by default

Noticed it is not falsey by default, I think it makes sense and would save some time in different projects. So proposing to add that too, what do you think?

[BUG] words is a const - should not be reassigned.

  const words = keywords || falsey.keywords;
  if (!Array.isArray(words)) words = [words];

should be let words = keywords || falsey.keywords;