The tcomb npm package is a library for Node.js and the browser which allows you to check the types of JavaScript values at runtime with a simple and concise syntax. It is useful for enforcing type safety, defining domain models, and creating composable and reusable type checkers.
Type Checking
This feature allows you to define a structure with specific types and create instances that adhere to those types.
const t = require('tcomb');
const Person = t.struct({ name: t.String, age: t.Number });
const person = Person({ name: 'Giulio', age: 43 });Function Argument Validation
This feature enables you to validate function arguments to ensure they are of the expected type.
const t = require('tcomb');
function sum(a, b) {
t.Number(a);
t.Number(b);
return a + b;
}
sum(1, 2);Subtyping
This feature allows you to create subtypes based on existing types with additional constraints.
const t = require('tcomb');
const Positive = t.subtype(t.Number, n => n >= 0);
const positiveNumber = Positive(10);Refinement
This feature is similar to subtyping but is specifically for refining types to a more specific subset.
const t = require('tcomb');
const Integer = t.refinement(t.Number, n => n % 1 === 0);
const integerNumber = Integer(42);Enums
This feature allows you to define a set of constants and ensure values match one of those constants.
const t = require('tcomb');
const Role = t.enums({ Admin: 'Admin', User: 'User' });
const userRole = Role('User');Prop-types is a library for React that is used to document the intended types of properties passed to components. It is similar to tcomb in that it provides runtime type checking, but it is specifically tailored for React's component props.
io-ts is a TypeScript runtime type system for IO decoding/encoding. It is similar to tcomb in providing runtime type checking and validation, but it leverages TypeScript's type system for added compile-time safety.
Joi is an object schema description language and validator for JavaScript objects. It provides a powerful and expressive way to define and validate data structures. It is similar to tcomb in terms of validation capabilities but has a different API and is often used for validating API input.
Ajv is a JSON schema validator. It validates data against JSON Schema standards and is similar to tcomb in terms of validation. However, it uses a JSON-based schema definition rather than a programmatic API.
array.forEach()
array.map()
array.some()
array.every()
Object.freeze()
Object.keys()
Setup di riferimento
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>gpr</title>
<!--[if lt IE 9]>
<script src="shims/json2.js"></script>
<script src="shims/es5-shim.min.js"></script>
<script src="shims/es5-sham.min.js"></script>
<script src="shims/html5shiv.min.js"></script>
<![endif]-->
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="gpr.js"></script>
</head>
<body>
<script type="text/javascript">
</script>
</body>
</html>
Una funzione T è un tipo se
T(values, [mut]) ove values è l'insieme di valori che occorrono per avere un'istanza di T (dipende da T) e mut indica se l'istanza è mutabile (default false)new T(new T(values)) equals new T(values)T.is(x) che restituisce true se x è un'istanza di Tda 2. deriva che T può essere usato come deserializzatore JSON di default
L'opzione name è utile per facilitare il debug.
var Point = struct({
x: Num,
y: Num
});
// i metodi vengono definiti normalmente
Point.prototype.toString = function () {
return '(' + this.x + ', ' + this.y + ')';
};
Come istanziare una struct
'use strict';
var p = new Point({x: 1, y: 2});
p.x = 2; // => TypeError, p è immutabile
p = new Point({x: 1, y: 2}, true);
p.x = 2; // ok, p ora è mutabile
Alcune meta informazioni
Point.meta = {
kind: 'struct',
props: props,
name: name
};
Restituisce true se x è un'istanza della struct.
Point.is(p); // => true
Restituisce un'istanza con le nuove proprietà senza modificare l'istanza originale.
Point.update(p, {x: 3}); // => new Point({x: 3, y: 2})
Definisce un'unione di tipi.
var Circle = struct({
center: Point,
radius: Num
});
var Rectangle = struct({
a: Point,
b: Point
});
var Shape = union([
Circle,
Rectangle
]);
// per poter usare Shape come costruttore occorre implementare dispatch()
Shape.dispatch = function (values) {
assert(Obj.is(values));
return values.hasOwnProperty('center') ?
Circle :
Rectangle;
};
var shape = new Shape({center: {x: 1, y: 2}, radius: 10});
Alcune meta informazioni
Shape.meta = {
kind: 'union',
types: types,
name: name
};
Restituisce true se x appartiene all'unione.
Shape.is(new Circle([p, 10])); // => true
Analogo ad una union con Nil e type.
var MaybeStr = maybe(Str);
MaybeStr.is('a'); // => true
MaybeStr.is(null); // => true
MaybeStr.is(1); // => false
Alcune meta informazioni
MaybeStr.meta = {
kind: 'maybe',
type: type,
name: name
};
Definisce una enumerazione (di stringhe).
var Direction = enums({
North: 0,
East: 1,
South: 2,
West: 3
});
Alcune meta informazioni
Direction.meta = {
kind: 'enums',
map: map,
name: name
};
Restituisce true se x appartiene dell'enum.
Direction.is('North'); // => true
Definisce un array di dimensione fissa le cui coordinate hanno i tipi specificati.
var Args = tuple([Num, Num]);
var a = new Args([1, 2]);
Alcune meta informazioni
Args.meta = {
kind: 'tuple',
types: types,
name: name
};
Restituisce true se x è una tupla corretta.
Args.is([1, 2]); // => true
Args.is([1, 'a']); // => false, il secondo elemento non è un Num
Args.is([1, 2, 3]); // => false, troppi elementi
Restituisce un'istanza con le nuove proprietà senza modificare l'istanza originale.
Args.update(a, 0, 2); // => [2, 2]
Definisce un sottotipo di un tipo già definito.
var Int = subtype(Num, function (n) {
return n === parseInt(n, 10);
});
var Q1Point = subtype(Point, function (p) {
// punti nel primo quadrante
return p.x >= 0 && p.y >= 0;
});
// uso del costruttore
var p = new Q1Point({x: -1, y: -2}); // => fail!
Alcune meta informazioni
Int.meta = {
kind: 'subtype',
type: type,
predicate: predicate,
name: name
};
Restituisce true se x è un'istanza corretta.
Int.is(2); // => true
Int.is(1.1); // => false
Definisce un array i cui elementi sono del tipo type.
var Path = list(Point);
// uso del costruttore
var path = new Path([
{x: 0, y: 0},
{x: 1, y: 1}
]);
Alcune meta informazioni
Path.meta = {
kind: 'list',
type: type,
name: name
};
Restituiscono un'istanza con le nuove proprietà senza modificare l'istanza originale.
Path.append(path, element, [mut]);
Path.prepend(path, element, [mut]);
Path.update(path, index, element, [mut]);
Path.remove(path, index, [mut]);
Path.move(path, from, to, [mut]);
// fa partire il debugger prima di lanciare un errore
// il debugger parte una volta sola perchè tipicamente dopo un fallimento
// ce ne possono essere molti altri e diventerebbe una noia
fail(message)
// se l'assert fallisce chiama fail(message)
assert(guard, [message])
// rende immutabili le proprietà dirette di un oggetto o un array
// a meno che unless sia = true
freeze(obj_or_arr, [unless])
// copia i campi di y in x. Se overwrite è falsy non è possibile
// sovrascrivere dei campi già presenti in x in modo da evitare
// fastidiosi bug
mixin(x, y, [overwrite])
// manipolazione degli array
append(arr, element);
prepend(arr, element);
update(arr, index, element);
remove(arr, index);
move(arr, from, to);
var Point3D = struct(mixin(Point.meta.props, {
z: Num
}));
var p = new Point3D({x: 1, y: 2, z: 3});
var c = new Circle({center: {x: 1, y: 2}, radius: 10});
// translate x by 1
var c2 = Circle.update(c, {
center: Point.update(c.center, {
x: c.center.x + 1
})
});
// (json, T, mut) -> instance of T
function decode(json, T, mut) {
if (T.fromJSON) {
return T.fromJSON(json, mut);
}
switch (T.meta.kind) {
case 'struct' :
var values = {};
var props = T.meta.props;
for (var prop in props) {
if (props.hasOwnProperty(prop)) {
values[prop] = decode(json[prop], props[prop], mut);
}
}
return new T(values, mut);
case 'union' :
assert(Func.is(T.dispatch));
return decode(json, T.dispatch(json), mut);
case 'maybe' :
return Nil.is(json) ? undefined : decode(json, T.meta.type, mut);
case 'tuple' :
return freeze(json.map(function (x, i) {
return decode(x, T.meta.types[i], mut);
}, mut));
case 'subtype' :
var x = decode(json, T.meta.type, mut);
assert(T.meta.predicate(x));
return x;
case 'list' :
return freeze(json.map(function (x) {
return decode(x, T.meta.type, mut);
}), mut);
default :
return json;
}
};
Copyright (C) 2014 Giulio Canti - Released under the MIT License.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
FAQs
Type checking and DDD for JavaScript
The npm package tcomb receives a total of 872,977 weekly downloads. As such, tcomb popularity was classified as popular.
We found that tcomb demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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