Meet npm Pro: unlimited public & private packages + package-based permissions.Learn more »

not-defined

2.1.0 • Public • Published

not-defined

checks if foo is not defined, i.e. undefined, null, an empty string, array, object or NaN

Installation | Usage | Annotated source | License

NPM version KLP

Installation

npm install not-defined

Usage

This snippet of code

const notDefined = require('not-defined')
 
if (notDefined(foo)) {
  // do something, usually throw a TypeError
}

is equivalent to the following pseudocode

if (foo is not defined, i.e. is not null, undefined, an empty string, array, object) {
  // do something, usually throw a TypeError
}

You can also use a shorter but still semantic form like

const no = require('not-defined')
 
if (no(foo)) {
  // do something, usually throw a TypeError
}

Follows a list of tested examples

no() // true
no(undefined) // true
no(null) // true
no('') // true
no([]) // true
no({}) // true
no(NaN) // true
 
no(0) // false
no(true) // false
no(false) // false
no('string') // false
no(['foo']) // false
no({ foo: true }) // false
no(42) // false
no(Infinity) // false
no(function () { return 1 }) // false

Pros

  • Type less.
  • Better readability (even your boss will understand your code ^:).
  • Can save bytes in your builds.
  • Easier to autocomplete in editors (for instance easier than typeof foo === 'undefined').

Annotated source

This is my first npm package written using KISS Literate Programming. It is plain ES5 function that is 159 characters long.

module.exports=function(x){return x==null||(typeof x == 'number'&&isNaN(x))||(x.length<1&&typeof x!='function')||(typeof x=='object'&&Object.keys(x).length<1)}

Snippet length<1 is used instead of equivalent length==0 to save two characters, considering it is used twice.

License

MIT

Install

npm i not-defined

DownloadsWeekly Downloads

125

Version

2.1.0

License

MIT

Unpacked Size

4.92 kB

Total Files

5

Last publish

Collaborators

  • avatar