instof
v0.0.1
Published
Tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an value.
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instof
instof(<value>,<constructor>) => <boolean>
instof(<value>,<constructor_name>) => <boolean>
Tests to see if the prototype property of a constructor appears anywhere in the prototype chain of an value.
This is an alternative to instanceof
that actually allows to check any value
not just objects, even primitives
, undefined
and null
.
Also the big advantage in comparance with instanceof
is that using instof
you can do check without explicit import of constructor to the module by specifying string name of it.
Usage
const instof = require('instof')
//=> true:
instof(undefined, 'Undefined')
instof(null, 'Null')
instof(global, 'Global')
instof(global, Object)
instof(window, 'Global')
instof(window, 'Window')
instof(window, 'EventTarget')
instof(window, 'Object')
instof(NaN, 'NotNumber')
instof(NaN, Number)
instof(NaN, 'Object')
instof(1/0, 'InfiniteNumber')
instof(-Infinity, 'InfiniteNumber')
instof(Infinity, Number)
instof(Object.create(null), 'Dictionary')
instof({}, Object)
instof(42, Number)
instof(42, 'Object')
instof('str', String)
instof('str', Object)
instof(async function () {}, 'AsyncFunction')
instof(async function () {}, Function)
instof(async function () {}, 'Object')
instof([], Array)
instof([], Object)
instof(new BigInt64Array(), 'BigInt64Array')
instof(new BigInt64Array(), 'TypedArray')
instof(new BigInt64Array(), Object)
//=> false:
instof(null, Object)
instof(Object.create(null), Object)
instof(BigInt(Number.MAX_SAFE_INTEGER), Number)
instof('str', Symbol)
instof({}, 'Dictionary')
instof(new Object(), 'Null')
instof([], 'TypedArray')
instof(new Int8Array(), Array)
Reserved constructor names
Reserved constructor names make possible to distinguish type of some special values from values with the real type.
Historically, accessing the global object has required different syntax in different JavaScript environments. On the web you can use window
, self
, frames
, in Node.js you must instead use global
and constructor of this global value is 'Object'. Also there are not straightforward situations with null
, NaN
and Infinity
values.
To determine the constructor of such values the instof
function uses the following constructor names:
- 'Undefined' for
undefined
- 'Null' for
null
- 'Global' for
global
,window
, etc. - 'NotNumber' for
NaN
- 'InfiniteNumber' for
Infinity
or-Infinity
- 'Dictionary' for object without prototype that was created by
Object.create(null)
Install
Install on Node.JS with npm
npm install instof
License
MIT © Taras Panasyuk