type-enforcement v1.0.18
Type Enforcement
Examples
Type Enforcement
is a js simple and flat library for class-based typing.
JavaScript dynamically typed and allows you to declare functions, objects, and variables without declaring a type. Although this feature simplifies the use of the language, it often requires the verification of input data. Type Enforcement
helps verify the types of transmitted values on the runtime.
Getting Started
Installation
To use Type Enforcement
in your project, run:
npm i type-enforcement
API docs
Table of Contents
- constructor: new TypeEnforcement(shema)
- te.validate(order, values, [options])
- te.normalise(order, values)
class: TypeEnforcement
Browser-compatible TypeEnforcement
class, implemented by following the ECMAScript® 2019 Language Specification
standard.
constructor: new TypeEnforcement(shema)
shema
[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) An object is an enumeration of rules of the formorder : rules
[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object).
In the code there can be more than one validation of the input data, so the rules are grouped into an order
.
Except for null
and undefined
, all primitive values have object equivalents that wrap around the primitive values:
- String for string primitive.
- Number for the number of the primitive.
- Boolean for the boolean primitive.
- Symbol for Symbol primitive.
- BigInt for the big number of the primitive.
Therefore, primitives can be declared via an object:
const TypeEnforcement = require('type-enforcement');
const te = new TypeEnforcement({
primitive: {
string: String,
number: Number,
boolean: Boolean,
symbol: Symbol
}
});
NOTE When using a
undefined
ornull
, an exception will be thrown.
In addition to primitives, you can use standard built-in objects and custom class, for example:
const TypeEnforcement = require('type-enforcement');
class MyClass {}
const te = new TypeEnforcement({
inline: {
object: Object,
invoke: Function,
regexp: RegExp,
array: Array,
date: Date,
error: Error,
promise: Promise
},
custom: {
class: MyClass
}
});
te.validate(order, values, options)
order
[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String) scheme name.values
[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) an object is an enumeration of the rules of the formfield: value
, wherefield
is the name of the value being validate, described inshema
.options
[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)skip
[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean) Theskip
option allows you to check only part of the values. Default:false
.
- returns: <Error | null>
Unlike the instanceof operator, this method validate if the value of the constructor.prototype
rule matches only on the current prototype
If all the values of the fields correspond to the scheme, then returns null
otherwise returns an error
.
const TypeEnforcement = require('type-enforcement');
const te = new TypeEnforcement({
'#example()': {
foo: Number,
bar: Array
}
});
function example(foo, bar) {
const err = te.validate('#example()', {
foo,
bar
});
if (err) {
throw err;
}
}
example('1'); // throw Error: Invalid value 'foo' in order '#example()'. Expected Number
example(1); // throw Error: Invalid value 'bar' in order '#example()'. Expected Array
example(1, []); // undefined
The te.validate
method is especially useful for implementing default parameters using the capabilities of ECMAScript® 2015 Language Specification
standard.
const TypeEnforcement = require('type-enforcement');
const te = new TypeEnforcement({
'#example()': {
foo: Number,
bar: Array
}
});
function example(foo = 0, bar = []) {
const err = te.validate('#example()', {
foo,
bar
});
if (err) {
throw err;
}
}
example(); // undefined
This only replaces undefined
values with defaults, which is sane. The skip
option allows you to check only part of the document, for example:
const TypeEnforcement = require('type-enforcement');
const te = new TypeEnforcement({
'#example()': {
foo: Number,
bar: Array
}
});
function example(foo, bar) {
const err = te.validate('#example()', { foo }, { skip: true });
// ↑ 'bar' field is omitted
if (err) {
throw err;
}
}
example('1'); // throw Error: Invalid value 'foo' in order '#example()'. Expected Number
example(1); // undefined
In the example above, the bar
field is omitted.
te.normalise(order, values)
order
[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)values
[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) An object is an enumeration of the rules of the formfield: value
, wherefield
is the name of the value being validate, described inshema
.- returns: [Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)
To normalize primitive types, properties of object analogs Primitive(value)
are used and a primitive. For other objects, an instance is created with the given value transferred to the constructor.prototype
, namely: new Class(value)
. The following example demonstrates the usefulness of te.normalise(order, values)
when using internetwork interoperability of applications.
const values = {
boo: true,
now: new Date()
};
const pack = JSON.stringify(values);
// '{"boo":true,"now":"2018-09-26T10:38:08.033Z"}'
// ^^^
// this is a string type
// ================ interworking ================
const TypeEnforcement = require('type-enforcement');
// Declaring rules
const te = new TypeEnforcement({
example: {
boo: Boolean,
now: Date
}
});
const json = JSON.parse(pack);
// {boo: true, now: "2018-09-26T10:38:08.033Z"}
// ^^^
// it's still a string type
const doc = te.normalise('example', json);
// { boo: true, now: 2018-09-26T10:35:41.345Z }
// ^^^
// this date type
console.log(doc);
The undefined
is a property of the global object; i.e., it is a variable in global scope. The initial value of undefined
is the primitive value undefined
. Note the following example:
Number(undefined); // NaN
Number(); // 0
In the author's opinion, such behavior is useful. The following example will demonstrate this behavior.
const TypeEnforcement = require('type-enforcement');
const te = new TypeEnforcement({
example: {
foo: Number,
bar: String
}
});
const values = te.normalise(example, {
foo: undefined,
bar: undefined
});
console.log(values); // { foo: 0, bar: '' }