# ducktype **Repository Path**: mirrors_josdejong/ducktype ## Basic Information - **Project Name**: ducktype - **Description**: Flexible data validation using a ducktype interface. For JavaScript and Node.js. - **Primary Language**: Unknown - **License**: Apache-2.0 - **Default Branch**: develop - **Homepage**: None - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 0 - **Created**: 2020-08-09 - **Last Updated**: 2026-02-07 ## Categories & Tags **Categories**: Uncategorized **Tags**: None ## README # ducktype Flexible data validation using a duck type interface for JavaScript and Node.js. As JavaScript is a loosely typed language, any variable can contain any type of data, and any type of data can be passed as arguments to any function. When dealing with data inputs coming from external sources, there is a need to validate the type and contents of the data. Ducktype offers an easy way to validate both basic data types as well as complex structured data types in a flexible way. Replace this kind of type checking mess: ```js function save (contact) { if (contact && isInteger(contact.id) && (contact.id > 0) && isString(contact.name) && contact.address && isString(contact.address.city) && isString(contact.address.street)) { // ... save contact } else { throw new Error('Invalid contact'); } } ``` with this: ```js var contactType = ducktype({ id: ducktype(Number, {integer: true, min: 0}), name: String, address: { city: String, street: String, } }); function save (contact) { contactType.validate(contact); // ... save contact } ``` ## Install ### npm ```sh npm install ducktype ``` ### bower ```sh bower install ducktype ``` ## Load ### Node.js ```js var ducktype = require('ducktype'); ``` ### browser ```html ``` ## Use ### Basic types ```js // use built-in types ducktype.number.test(2.3); // true ducktype.number.test('hi'); // false ducktype.number.test(true); // false ducktype.date.test(new Date()); // true ducktype.date.test(2.3); // false ducktype.string.test('hello'); // true // create a ducktype var type = ducktype(Number); type.test(2.3); // true type.test('hi'); // false type.test(true); // false // create a ducktype with options var nullableString = ducktype(String, {nullable: true}); nullableString.test('string'); // true nullableString.test(null); // true nullableString.test(2.3); // false ``` ### Combined types ```js // combination of types var combi = ducktype(Number, String); combi.test(2.3); // true combi.test('hi'); // true combi.test(true); // false ``` ### Structured objects ```js // structured object var person = ducktype({ name: String, age: Number, address: { city: String, street: String, country: String }, email: ducktype(String, {optional: true}) }); person.test({ name: 'John', age: 32, address: { city: 'Sunnyvale, CA 95125', street: '701 First Ave.', country: 'United States' } }); // true person.test({ name: 'Mary', age: 26 }); // false ``` ### Structured Arrays ```js // structured arrays var numberArray = ducktype([Number]); numberArray.test([1, 2, 3]); // true numberArray.test([1, 'string', 3]); // false // structured object and array var family = ducktype({ name: String, age: ducktype(Number, {optional: true}), children: [ { name: String, age: ducktype(Number, {optional: true}) } ] }); family.test({ name: 'John', children: [ { 'name': 'Mary', 'age': 6 }, { 'name': 'Grant' } ] }); // true family.test({ name: 'John', children: [ { 'firstName': 'Mary', 'age': 6 }, { 'firstName': 'Grant' } ] }); // false ``` ### Function arguments ```js var type = ducktype([Number, Number]); function add (a, b) { type.validate(arguments); return a + b; } var sum = add(2, 3); // ok var sum = add(2, 'string'); // will throw a TypeError ``` Alternatively, a ducktype wrapper can be created which validates the function arguments against the ducktype: ```js var add = ducktype([Number, Number]).wrap(function add (a, b) { return a + b; }); var sum = add(2, 3); // ok var sum = add(2, 'string'); // will throw a TypeError ``` ## API ### construction A ducktype can be constructed as: ``` ducktype(type) ducktype(type, options) ducktype(type1, type2, ...) ducktype(type1, type2, ..., options) ``` Where: - `type` can be: - A basic type. Choose from `Array`, `Boolean`, `Date`, `Function`, `Number`, `Object`, `RegExp`, `String`, `null`, `undefined`. - Another ducktype. - An object. All properties of the object will be checked. Each property can be a basic type, ducktype, object, or array. - An array. An array can have zero, one or multiple elements which can be a basic type, ducktype, object, or array. Providing an array with *zero* elements will just return a `ducktype(Array)`. Providing an array with *one* element will return a ducktype which will test each of tested arrays elements against the given type, for example `ducktype([Number]).test(1, 2, 3)`. Providing an array with *multiple* elements will validate the length of the tested array, and validate each of the array elements one to one against the provided types. This can be used to test the number and type of function arguments. Example: `ducktype([Number, String]).test(2, 'str')`. - `options` is an object which can contain properties: - A string `name` - A boolean `optional` - A boolean `nullable` - A boolean `integer`. Test whether a number has an integer value. Only applicable for Numbers. - A number `min`. Test whether a number is larger or equal to a minimum value. Only applicable for Numbers. - A number `max`. Test whether a number is smaller or equal to a maximum value. Only applicable for Numbers. A created ducktype has functions: - `test(object)`. A function which returns true when provided object matches the ducktype, and false otherwise. - `validate(object)`. A function which will throw a TypeError when the provided object does not match the ducktype. - `wrap(fn)`. Creates a wrapper function around the provided function, which validates the function arguments against the ducktype. Only applicable for ducktypes containing an array, as the ducktype is tested against an array with the function arguments. ### Built-in types Ducktype comes with a set of built-in types: - `ducktype.array` - `ducktype.boolean` - `ducktype.date` - `ducktype.email` - `ducktype.integer` - `ducktype.function` - `ducktype.number` - `ducktype.object` - `ducktype.regexp` - `ducktype.string` - `ducktype.null` - `ducktype.undefined` - `ducktype.url` The built-in types can be used as: ```js ducktype.number.test(2.3); // true ducktype.string.test(2.3); // false ``` ## Test To execute tests for the library, run: npm test ## Roadmap - Implement more options for specific types: - Number: finite, odd, even, positive, negative, nan, ... - String: lowercase, uppercase, alpha, alphanumeric, empty, ... - Array: length, length.min, length.max, ... - Implement a parser accepting a string describing a type in [annotations](https://developers.google.com/closure/compiler/docs/js-for-compiler#types). - Implement support to define your own tests for custom types. - Implement non-strict type checking: when an object can be converted to the desired type, it is ok. For example a string containing a numeric value can be considered a valid Number, or a string containing an ISO date can be considered a valid Date. ## License Copyright (C) 2013-2020 Jos de Jong Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.