robloach/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 value is falsey. Works for strings, arrays and arguments objects with a length of 0, and objects with no own enumerable properties are considered falsey.

Install with npm

npm i falsey --save

What makes this lib unique is the option to pass an array of values that should always evuate as "falsey". For example, you might want to allow users to define nil or nope to disable something.

Usage

var isFalsey = require('falsey');
console.log(isFalsey('');
//=> `true`

Examples

All of the following return true

isFalsey(undefined);
isFalsey(null);
isFalsey(false);
!isFalsey(true);
isFalsey(0);
!isFalsey(1);
isFalsey('');
!isFalsey('1');
isFalsey(NaN);
isFalsey({});
!isFalsey({a: 'b'});
isFalsey([]);
!isFalsey([0]);

Special cases

There are only four "special cases", ['false', 'none', 'nil', 'null], and these are easily overridden by passing a value as a second parameter, e.g.

isFalsey(foo, []);

// other examples...
isFalsey('false');
!isFalsey('false', []); // override special cases
!isFalsey('true');
isFalsey('nil');
!isFalsey('nil', []); // override special cases
isFalsey('none');
!isFalsey('none', []); // override special cases
isFalsey('null');
!isFalsey('null', []); // override special cases

Or, pass an array of values that should return true when evaluated as falsey:

isFalsey(foo, ['no', 'nope', 'nada', 'zilch']);
// you get the point

Related

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

Contributing

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

Running tests

Install dev dependencies.

npm i -d && npm test

Author

Jon Schlinkert

• github/jonschlinkert
• twitter/jonschlinkert

License

Copyright (c) 2015 Jon Schlinkert
Released under the MIT license

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This file was generated by verb-cli on March 07, 2015.