isit

    1.1.0 • Public • Published

    isit

    A Node.js module that tests a value’s type against a string like 'positive integer' or 'non-empty map'.

    Installation

    npm install isit --save

    Usage

    When calling isit(), the first argument is a space-separated string of type tests, and the second argument is the value to be tested. isit() returns true only if all tests pass.

    const isit = require('isit')
    isit('non-empty array', [1, 2, 3]) // true
    isit('empty map', new Map()) // true
    isit('positive integer', 1) // true

    Available tests are listed in the “Type Tests” section below. Anything that does not match one of the available tests will be considered a class name (example: map in the above code block).

    Negation

    A test can be individually negated by prefixing it with non- or !, as in:

    const isit = require('isit')
    isit('non-empty array', [1, 2, 3]) // true
    isit('array !empty', [1, 2, 3]) // true
    isit('empty non-array', '') // true

    Create Curried Functions

    If you omit the second argument, a function is returned which runs the test provided in the first argument.

    const isObject = require('isit')('non-array object')
    isObject({}) // true
    isObject([]) // false

    Individual Test Functions

    All tests are also available as member functions of isit, allowing you to run a single test like so:

    const isit = require('isit')
    isit.array([]) // true
     
    const isString = require('isit').string
    isString('test') // true

    Type Tests

    Here is the complete list:

    • arguments / args
    • array
    • blank
    • boolean / bool
    • boolish
    • buffer
    • collection
    • empty
    • false
    • falsey
    • float
    • finite
    • function
    • generator
    • infinity
    • integer / int
    • iterable
    • nan
    • negative
    • nil
    • null
    • number
    • numberish
    • numeric
    • object
    • objectbased
    • plain
    • positive
    • primitive
    • scalar
    • string
    • stringish
    • symbol
    • true
    • truthy
    • typedarray
    • undefined / undef

    Undefined & Null

    Value: undefined
    undef
    null nil
    undefined
    null

    Primitives & Scalars

    Value Type: primitive scalar
    Undefined
    Null
    Boolean
    Number
    String
    Symbol
    Object
    Function

    Booleans

    Value: boolean
    bool
    boolish
    true
    false
    'true' string
    'false' string
    new Boolean(true)
    new Boolean(false)
    Value: true truthy
    true
    new Boolean(true)
    'true' string
    'false' string
    1
    'test'
    []
    Value: false falsey
    false
    new Boolean(false)
    'false' string
    0
    ''

    Empty Values

    Every empty-checker out there assesses “emptiness” a bit differently. For our purposes, an empty value is one which contains no useful information except the absence of a value. Therefore, unlike many similar functions, the empty test does not consider 0, false, or zero-parameter functions to be “empty,” because these can often be intended as actual values.

    Value: empty
    undefined
    null
    NaN
    0
    false
    ''
    {}
    []
    () => {}
    new Error()
    new Map()
    new Set()

    Blank Values

    The blank test is the same as empty except it also returns true for strings that consist only of whitespace.

    Functions

    Value: function generator
    function () {}
    () => {}
    function* () {}

    Numbers

    Value: number numberish numeric
    0
    1.23
    new Number(1)
    '1'
    '1e3'
    NaN
    Value: positive negative
    Infinity
    123.45
    0
    -0
    -123.45
    -Infinity

    JavaScript considers the number zero to be either positively or negatively signed; therefore, positive reports true for 0. If you want to exclude zero, consider using a simple x>0 test instead.

    More Number Tests:

    • nan
    • integer / int
    • float
    • finite
    • infinity

    Objects

    Although functions are technically objects in JavaScript, they are often considered a separate category because the typeof operator gives them their own type. Use objectbased if you want to include functions.

    Value: object objectbased
    {}
    () => {}
    Value: object plain array
    new Date()
    {}
    []

    The object test returns true for arrays, because arrays are objects in JavaScript. If you want to exclude arrays, test against 'non-array object' instead.

    Arguments

    arguments or args returns true if the value is an Arguments object.

    Buffers

    The buffer test returns true if the value is a Node.js or Browserify Buffer.

    Collections

    The collection test returns true if the value is an instance of one of:

    • Map
    • Set
    • WeakMap
    • WeakSet

    Iterables

    The iterable test returns true if for...of can be used to iterate through the value.

    Typed Arrays

    The typedarray test returns true if the value is an instance of one of:

    • Int8Array
    • Uint8Array
    • Uint8ClampedArray
    • Int16Array
    • Uint16Array
    • Int32Array
    • Uint32Array
    • Float32Array
    • Float64Array

    Strings

    Value: string stringish
    ''
    'test'
    new String('test')

    Symbols

    The symbol test returns true if the value is a symbol.

    Class Testing

    You can use isit.a or isit.an to see if an object is an instance of a given class.

    You can provide the class itself or the class name as a case-insensitive string.

    const isit = require('isit')
     
    isit.a(Date, new Date()) // true
    isit.a('date', new Date()) // true
     
    isit.an(Error, new Error()) // true
    isit.an('error', new Error()) // true
     
    // Returns true because TypeError extends Error
    isit.an(Error, new TypeError()) // true

    You can also check if a given value is an instance of any one of a list of classes:

    const isit = require('isit')
     
    isit.a([TypeError, ReferenceError], new TypeError()) // true
    isit.a('TypeError ReferenceError', new TypeError()) // true

    Advanced Usage

    Adding or Overriding Tests

    You can add new tests, or override existing ones, by requiring isit/x and calling it as a function with the additional tests as an object argument. For example:

    const isit = require('isit/x')({
      zero: value => value === 0
    })
    isit('negative zero', -0) // true
    isit('non-zero integer', 1) // true

    Install

    npm i isit

    DownloadsWeekly Downloads

    12

    Version

    1.1.0

    License

    MIT

    Last publish

    Collaborators

    • lamansky