type-quickly 3.0.0 / type-robustly 2.0.0

NPMs fastest, most comprehensive, and most correct typing packages for node and the browser

If you want only the quick rundown, read the Comprehensive/Usage/Properties-of-is sections.

1. See https://github.com/Meouzer/Typing for extensive typing information. This is your definitive typing resource.
2. If you are coding in a node environment only and just want type checkers for the built-in ES6 classes, use of node's util.types.isKlass(x) functions is the best option.
   • This package's type checkers also work in the browser.
3. The only difference between type-quickly and type-robustly is that the latter correctly types edge cases of the ES6 built-in classes at the cost of a 57% reduction in speed.
   • Even so, type-robustly is still faster than all other competitors save one. That one, like all other competitors, is highly limited in what it will correctly type.

Competitors' Technique

Competitors rely on use of Object.prototype.toString(), constructor names, or instanceof with results that do not work unless your world is narrowed down to objects of the form new Klass(...), where most of the time Klass is restricted to being a built-in class. The toString() function has serious problems including the fact that doesn't work for programmer defined classes.

Competitors use toString()/constructors/instanceof to search the first dimension to pin down an object to a particular class, say Boolean, but leave the type at "Boolean" because the second dimension is not searched by determining where the object lies in the downward inheritance chain of Boolean.prototype: is the object Boolean.prototype itself, which must be typed to "Object"? is the object one degree away from Boolean.prototype so it should be typed to "Boolean"? or is it further away, so it should be typed to "Object"?

Author's Technique

To search along the second dimension, the internal prototype of the object can be examined. Even though this idea is obvious, no one has successfully implemented it until now: see the Constructor/Prototype Approach to Typing appendix to see how it's done.

However, the constructor/prototype technique is slow, and the author came up with something even better: the prototyping technique, which is lightning fast and avoids all the problematics of toString() and constructor names. Basically you figure out the best typing function that types Boolean.prototype and all objects derived from it. Then do the same for all other classes and fit the small typing functions together inside a function to rule them all.

Extremely Fast and Correct

This package's combination of speed and correctness blows the competition away with gale force winds. Hundreds of tests show this package is 100% correct: See https://github.com/Meouzer/Typing -- type-quickly 3.0.0 -- Tests. A number of typing packages are compared against type-quickly in following tables. There are other packages, but the best were chosen.

| typing package | numbertimesfastertype-quicklyis | typesES6built-inclassinstances? | typessecondaryobjects? | types4programmerclassinstances? | |--------------------|-------------------------------------------------|-------------------------------------------------|--------------------------------|--------------------------------------------------------| | type-quickly |   | ✅ | ✅ | ✅ | | type-robustly | 2.3 | ✅ | ✅ | ✅ | | kind-of | 33 | ❌1 | ❌ | ❌ | | type-detect | 3.4 | ❌1 | ❌ | ❌ | | types.js | 24 | ❌2 | ❌ | ❌ | | data-type | 2.4 | ❌2 | ❌ | ❌ | | whats-the-type | 15.7 | ✅ | ❌ | ✅ | | which-builtin-type | 1599 | ✅ | ❌3 | ✅ | | just-typeof | 2.7 | ❌1 | ❌ | ❌ | | type-name | 4.4 | ✅ | ❌ | ✅ | | easytype | 1.7 | ❌1 | ❌ | ❌ |

✅ = yes. ❌ = no. (1) variant error classes incorrectly typed. (2) errors are extensive. possibly designed with only ES5 in mind. (3) sometimes correct, sometimes not. (4) example of programmer class instance: const x = new Foo() where Foo is a programmer defined class.

Speed comparisons are based on testing each package's typing function on x = new Boolean(true). Whenever, a competitor slows down on another class due to more complicated logic, type-quickly will be even faster in comparison because type-quickly does not slow down.

Examples of mistakes that all competitors make is to type Boolean.prototype or secondary objects such as Object.create(new Boolean(true)) to "Boolean". If you think that doesn't matter, think again: Array.isArray() and node's type checkers work correctly on the class prototype and all objects derived from it.

Comprehensive

The type-quickly/type-robustly packages are the most comprehensive typing packages on NPM because they alone type everything in ES6 (and more) correctly, including the following sometimes overlapping categories.

1. All ES6 = ECMA-2015 classes
2. Node-Classes: 100+ classes such as node_buffer_Buffer, node_buffer_Blob, node_stream.Readable, node_http.Server; etc.
3. JavaScript Classes beyond ES6: Blob, Headers, ReadableStream, etc.
4. Secondary-objects, which are objects created with Object.create()
5. Class prototypes
6. Null-objects, which are objects not deriving from Object.prototype, e.g., Object.create(null) and its derivations.
7. Programmer defined classes
   • All objects derived from the class prototype, including the class edge-case (see The Edge Case appendix)
8. Edge-cases of built-in ES6 classes (type-robustly only)
9. Windows and DOM objects

| type package | typessecondaryobjects? | typesclassprototypes? | types3programmerdefinedclasses? | typesDOMobjects? | |--------------------|--------------------------------|-------------------------------|--------------------------------------------------------|--------------------------| | type-quickly | ✅ | ✅ | ✅ | ✅ | | type-robustly | ✅ | ✅ | ✅ | ✅ | | kind-of | ❌ | ❌ | ❌ | ❌ | | type-detect | ❌ | ❌ | ❌ | ❌ | | types.js | ❌ | ✅1 | ❌ | ❌ | | data-type | ❌ | ❌ | ❌ | ❌ | | whats-the-type | ❌ | ❌ | ❌ | ❌ | | which-builtin-type | ❌ | ❌2 | ❌ | ❌ | | just-typeof | ❌ | ❌ | ❌ | ✅ | | type-name | ❌ | ❌ | ❌ | ✅ | | easytype | ❌ | ❌ | ❌ | ✅ |

✅ = yes. ❌ = no. (1) just one mistake for built-in ES6 classes (2) sometimes correct, sometimes not (3) programmer defined classes: class prototype and all objects derived from it must be typed correctly

Usage

Import for Node

const {type, is} = require('type-quickly')
-------------------------------------------------------------------------

Import for Browser

<script src="node_modules/type-quickly/type-quickly.js"  
    type="text/javascript"></script>
    
or copy type-quickly.js anywhere and link to it    
-------------------------------------------------------------------------

ES6 classes:

Boolean; Number; String; Date; RegExp; Array; Int8Array; Uint8Array;
Uint8ClampedArray; Int16Array; Uint16Array; Int32Array; Uint32Array;
Float32Array; Float64Array; BigInt64Array; BigUint64Array; Error;
URIError; EvalError; RangeError; ReferenceError; SyntaxError; TypeError;
WeakSet; Set; WeakMap; Map; ArrayBuffer; DataView; Promise;

// Map objects (Map.prototype or objects deriving from it)

const x = new Map();             
const prototype = Map.prototype;  
const secDegObj = Object.create(x);

// They are correctly typed
type(x)             "Map"
type(prototype)     "Object"
type(secDegObj)     "Object"

is.Map(x)           true
is.Map(prototype)   false
is.Map(secDegObj)   false
------------------------------------------------------------------------

Boxed Primitives

const boxedSymbol = Object(Symbol)
const boxedBigInt = Object(BigInt(7))
const boxedBoolean = new Boolean(true)

type(boxedSymbol)                "boxedSymbol"
type(boxedBigInt)                "boxedBigInt"
type(boxedBoolean)      i        "Boolean"
is.boxedSymbol(boxedSymbol)      true
is.boxedBigInt(boxedBigInt)      true
is.boxedPrimitive(boxedSymbol)   true
is.boxedPrimitive(boxedBoolean)  true

-------------------------------------------------------------------------

JavaScript classes beyond ES6 for node and the browser: some were 
originally defined in node, in which case they are now global in node.  

AggregateError; AbortController; AbortSignal; Blob; 
ByteLengthQueuingStrategy; BroadcastChannel; CompressionStream; 
CountQueuingStrategy; CryptoKey; DecompressionStream; Event; EventTarget; 
FormData; Headers; MessageChannel; MessageEvent; MessagePort; 
PerformanceEntry; PerformanceMeasure; PerformanceObserver; 
PerformanceObserverEntryList; PerformanceResourceTiming; 
ReadableByteStreamController; ReadableStream; ReadableStreamBYOBReader; 
ReadableStreamDefaultController; ReadableStreamDefaultReader; 
SharedArrayBuffer; TextDecoderStream; TextEncoder; TextEncoderStream; 
TransformStream; TransformStreamDefaultController; URL; URLSearchParams; 
WritableStream; WeakRef; WritableStreamDefaultController; 
WritableStreamDefaultWriter;

const x = new Blob();

type(x)                 "Blob" in node and browser
is.Blob(x)              true   in node and browser
is.node_buffer_Blob(x)  true in node environment since
                        Blob is defined at node.buffer.                        
-------------------------------------------------------------------------

Node Environment only. Node classes that are not JavaScript globals.

const fs = require('fs');
const x = new fs.WriteStream("xyz.txt");

type(x)                     "node_fs_WriteStream"
is.node_fs_WriteStream(x)   true

The is.node_fs_WriteStream() function is not available for the browser.

Typing Programmer Defined Classes

Programmer defined classes are correctly typed out of the box, assuming the programmer always insures the constructor is correct, i.e., Klass.prototype.constructor must be Klass. Internally, the type(x) function uses a constructor/prototype technique, which is slow. However, if you want to bypass this slowness and make typing a programmer defined class lightning fast, then there are two typing protocols. Both work even if the constructor is not properly set.

Protocol-1 is preferable since it at no cost handles edge cases of the class in the type() and dtype() functions.

Protocol-1 for Typing Programmer Defined Classes

For a programmer defined class Klass, simply write (1) type.asInstance(this, "Klass") inside the constructor and (2) type.asClass(Klass) outside the constructor. Edge cases are most excellently handled.

function Klass()
{    
    // (1) Make sure type() works correctly on Klass objects:
    // Klass.prototype and all objects derived from it.
    
    type.asInstance(this, "Klass");
}

// If you redefine Klass.prototype, make sure (2)
// succeeds not preceeds it. 

Klass.prototype = ...
    
// (2) Provide an is.Klass() function and make
// sure dtype() handles Klass edge cases. 

type.asClass(Klass)

// Klass objects 
// (Klass.prototpe and objects derived from it)

const x = new Klass()                 
const prototype = Klass.prototype     
const edgeCase = Object.create(Klass.prototype)
const secDegObj = Object.create(x);

// They are typed correctly.

type(x)             "Klass"
type(prototype)     "Object"
type(edgeCase)      "Object"
type(secDegObj)     "Object"

is.Klass(x)          true
is.Klass(prototype)  false
is.Klass(edgeCase)   false
is.Klass(secDegObj)  false  

Protocol-2 for Typing Programmer Defined Classes

Protocol-2 is deprecated unless protocol-1 is unfeasible for some odd reason, e.g., there is no access to the inside of the constructor.

To type a programmer defined class Klass, write type.thisClass(Klass) outside the constructor. Edge cases will be incorrectly typed to "Klass" by both type() and dtype().

function Klass()
{    
}

// Make sure Klass objects, except for the edge case 
// are type correctly. Again must be written after
// any redefinition Klass.prototype. 

type.thisClass(Klass)

// Klass objects 
const x = new Klass()                 
const prototype = Klass.prototype     
const edgeCase = Object.create(Klass.prototype)
const secDegObj = Object.create(x);

type(x)             "Klass"
type(prototype)     "Object"
type(edgeCase)      "Klass" (incorrect)
type(secDegObj)     "Object"

is.Klass(x)           true
is.Klass(prototype)   false
is.Klass(edgeCase)    true (incorrect)
is.Klass(secDegObj)   false

Exports

| Export | Description | |------------|-------------------------------------------------------------------------------------------| | type(x) | Robust and very fast typing function. | | is | Object whose function properties test for various data types, amongst other capabilities. | | dtype(x) | Details the inheritance chain of x. See dtype(x) appendix. |

Properties of the is Object

| test | description | |--------------------------------|-------------------------------------------------------------------------------------------| | non typing || | is.configurable(x,prop) | is the property prop of x configurable? returns true if property not existent on x. | | is.writable(x,prop) | is the property prop of x writable? returns true if property not existent on x. | | is.enumerable(x,prop) | is the property prop of x enumerable? returns false if property not existent on x. | | is.ownProperty(x,p) | is p a property directly defined on x? | | is.nodeEnvironment() | is running in Node.js as opposed to Browser? | | is.browserEnvironment() | is running in Browser as opposed to Node.js? | | is.nativeCode(func) | is func a built-in JavaScript function or method?(built-ins have native code) | | typing || | is.domObject(x) | is x a document or DOM object? | | is.nullObject(x) | is x a null-object? | | is.arguments(x) | is x a function's arguments list? | | is.classPrototype(x) | is x a function's prototype? | | is.Object(x) | is x an object? | | is.primitive(x) | is x a primitive? | | is.boxedPrimitive(x) | is x a Boolean, Number, String, boxed symbol, or boxed bigint? | | is.errorVariant(x) | is x a class instance of Error or other variant Error class? | | is.typedArray(x) | is x a class instance of a typed array class? | | is.boolean(x) | is x a boolean? | | is.number(x) | is x a number? | | is.string(x) | is x a string? | | is.bigint(x) | is x a bigint? | | is.BoxedBigInt(x) | is x a boxed bigint? , e.g., like Object(BigInt(7)) | | is.symbol(x) | is x a symbol? | | is.BoxedSymbol(x) | is x a boxed symbol? , e.g., like Object(Symbol()) | | is.Function(x) | is x a function? | | is.mapIterator(x) | is x a Map iterator? | | is.setIterator(x) | is x a Set iterator? | | is.arrayIterator(x) | is x an Array iterator? | | is.stringIterator(x) | is x a String iterator? | | is.generatorFunction(x) | is x a generator function? | | is.generatorObject(x) | is x a generator object? | | is.asyncFunction(x) | is x an async function? | | is.arrayBufferView(x) | wrapper around ArrayBuffer.isView(x) | | is.Klass (x) | is x a class instance of Klass? Klass may be a built-in or programmer defined class. | | is.node_abc_..._Klass(x) | is x a class instance of the node class whose complete path is node_abc_..._Klass? |

Note the difference between is.boolean(x) and is.Boolean(x), which check for the primitive boolean and class instance of Boolean respectively. Also boxed symbols and boxed bigints type to "boxedSymbol" and "boxedBigInt" respectively.

Concerning is.ownProperty(x,p), this function works correctly even if x is a null-object. x.hasownProperty(p) fails if x is a null-object because hasOwnProperty is defined on Object.prototype from which x does not inherit.

Appendices

Browser Support

The IE11 browser is not supported as it is too out of date and is now defunct. Testing has passed in Chrome, Edge, Firefox, and Opera.

The definitive typing Function dtype(x)

This typing function gives the most detail possible by describing the inheritance chain of x. This function requires enforcement of the constructor protocol: that Klass.prototype.constructor is Klass for each programmer defined class Klass.

| Expression | Meaning | |---------------------------------|---------------------------------------------------------------------------| | x is a Klass-object of degree n | x is n steps away from Klass.prototype | | x is an object of degree n | x is n steps away from Object.prototype | | x is a null object of degree n | x does not inherit from Object.prototpe and is n steps away from null |

Of course, stepping is done in the inheritance chain of x.

| dtype(x) | x | |-----------------------|----------------------------------------------------------------------| | "Klass[Prototype]" | x is Klass.prototype | | "Klass" | x is a class instance of Klass | | "Klass[Object]" | x is a Klass object of degree 1, but not a class instance of Klass | | "Klass[Object(n)]" | x is a Klass object of degree n = 2,3,.... | | "Null[Object]" | x is a null-object of degree 1 | | "Null[Object(n)]" | x is a null-object of degree n = 2,3,... | | "Object[Prototype]" | x is Object.prototpe | | "Object" | x is an object of degree 1 | | "Object(n)" | x is an object of degree n = 2,3,... |

Since the inheritance chain of x may contain more than one class prototype, where classes are to include the imaginary Object class and the imaginary Null class, the specificity rule applies: dtype(x) is required to be the most informative choice: the nearest class prototype is used.

If typing protocol-1 is followed, then the edge case is correctly typed to Klass[Object].

const {dtype} = require('type-quickly');

function Klass()
{        
}

// make sure constructor protocol is followed: that
// the following is true.    
Klass.prototype.constructor === Klass

// Klass objects
const instance = new Klass();
const prototype = Klass.prototype;
const edgeCase = Object.create(Klass.prototype);
const deg2Obj = Object.create(Object.create(Klass.prototype);
const deg3Obj = Object.create(Object.create(instance);

dtype(instance)     "Klass"
dtype(prototype)    "Klass[prototype]"
dtype(edgeCase)     "Klass[Object]"     (typing protocol-1 followed)
dtype(edgeCase)     "Klass" (incorrect) (typing protocol-1 not followed)
dtype(deg2Obj)      "Klass[Object(2)]"
dtype(deg3Obj)      "Klass[Object(3)]"        

Constructor/Prototype Approach to Typing

A constructor/prototype approach to typing works as long as programmers make sure class constructors are set correctly: Klass.prototype.constructor should be Klass. A typing function must type class prototypes and all objects deriving from class prototypes correctly.

function typeIt(x)
{
    if (x === null) return "null";
    const tof = typeof(x);
    if(tof === 'function')
    {
        if(x === Function.prototype) return "Object";
        return "Function";
    }
    if (tof !== 'object') return tof;
    const proto = Object.getPrototypeOf(x);
    if(proto === null) return "Object"
    if(proto === BigInt.prototype || proto === Symbol.prototype 
        || proto === Function.prototype) return "Object";
    if(x.constructor !== proto.constructor
        && typeof(x.constructor) === "function"
        && x === x.constructor.prototype) return "Object";
    const Klass = proto.constructor;
    if(Klass === undefined) return "Object";
    if(proto === Klass.prototype) return Klass.name;
    return "Object";
}

The Edge Case

The edge case of a class Klass is edgeCase = Object.create(Klass.prototype) that isn't to be used as a class prototype itself nor to be modified to become a class instance of Klass via a call to Klass.call(x,...) or Klass.apply(x,[...]).

No typing function discussed in this readme file correctly types edge cases of the built-in classes. That's because edge cases seem to have no reason for existence, and taking edge cases of built-in classes into account would slow down code for no great reason. However, we do take edge cases of programmer defined classes into account because there is no cost to typing them correctly.

The author's type-robustly package does take edge cases of the ES6 built-in classes into account. If you think edge cases do matter, then type-robustly is your only possible package. In any case, the dtype() function of type-robustly is great for diagnostics, as it traces out the inheritance chain, and is in fact used by deep-copy-diagnostics. Deep copy packages on NPM will make the mistake of copying a class instance into an edge case and visa-versa. Only use of dtype() of the type-robustly package will uncover these and other deep-copying mistakes.

Unfortunately, there is no good way to correctly type edge cases of JavaScript classes beyond ES6. Object.prototype.toString() is too much of a mess even in ES6, and goes completely defunct beyond ES6, while such classes do not provide methods that can be innocuously called for testing. The best you can do is to verify the existence of required properties, which of course can be spoofed.