13 | title: Metadata Proposal - ECMAScript 14 | status: proposal 15 | location: https://rbuckton.github.io/reflect-metadata 16 | copyright: false 17 | contributors: Ron Buckton 18 |19 | 20 |
Proposal to add Metadata to ECMAScript.
24 |
30 | // define metadata on an object or property
31 | Reflect.defineMetadata(metadataKey, metadataValue, target);
32 | Reflect.defineMetadata(metadataKey, metadataValue, target, propertyKey);
33 |
34 | // check for presence of a metadata key on the prototype chain of an object or property
35 | let result = Reflect.hasMetadata(metadataKey, target);
36 | let result = Reflect.hasMetadata(metadataKey, target, propertyKey);
37 |
38 | // check for presence of an own metadata key of an object or property
39 | let result = Reflect.hasOwnMetadata(metadataKey, target);
40 | let result = Reflect.hasOwnMetadata(metadataKey, target, propertyKey);
41 |
42 | // get metadata value of a metadata key on the prototype chain of an object or property
43 | let result = Reflect.getMetadata(metadataKey, target);
44 | let result = Reflect.getMetadata(metadataKey, target, propertyKey);
45 |
46 | // get metadata value of an own metadata key of an object or property
47 | let result = Reflect.getOwnMetadata(metadataKey, target);
48 | let result = Reflect.getOwnMetadata(metadataKey, target, propertyKey);
49 |
50 | // get all metadata keys on the prototype chain of an object or property
51 | let result = Reflect.getMetadataKeys(target);
52 | let result = Reflect.getMetadataKeys(target, propertyKey);
53 |
54 | // get all own metadata keys of an object or property
55 | let result = Reflect.getOwnMetadataKeys(target);
56 | let result = Reflect.getOwnMetadataKeys(target, propertyKey);
57 |
58 | // delete metadata from an object or property
59 | let result = Reflect.deleteMetadata(metadataKey, target);
60 | let result = Reflect.deleteMetadata(metadataKey, target, propertyKey);
61 |
62 | // apply metadata via a decorator to a constructor
63 | @Reflect.metadata(metadataKey, metadataValue)
64 | class C {
65 | // apply metadata via a decorator to a method (property)
66 | @Reflect.metadata(metadataKey, metadataValue)
67 | method() {
68 | }
69 | }
70 |
71 | // Design-time type annotations
72 | function Type(type) { return Reflect.metadata("design:type", type); }
73 | function ParamTypes(...types) { return Reflect.metadata("design:paramtypes", types); }
74 | function ReturnType(type) { return Reflect.metadata("design:returntype", type); }
75 |
76 | // Decorator application
77 | @ParamTypes(String, Number)
78 | class C {
79 | constructor(text, i) {
80 | }
81 |
82 | @Type(String)
83 | get name() { return "text"; }
84 |
85 | @Type(Function)
86 | @ParamTypes(Number, Number)
87 | @ReturnType(Number)
88 | add(x, y) {
89 | return x + y;
90 | }
91 | }
92 |
93 | // Metadata introspection
94 | let obj = new C("a", 1);
95 | let paramTypes = Reflect.getMetadata("design:paramtypes", obj, "add"); // [Number, Number]
96 | When the abstract operation GetOrCreateMetadataMap is called with Object _O_, property key _P_, and Boolean _Create_ the following steps are taken:
106 |All ordinary objects have an internal slot called [[Metadata]]. The value of this internal slot is either *null* or a *Map* object and is used for storing metadata for an object.
130 |When the [[HasMetadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_ and property key _P_, the following steps are taken:
133 |When the abstract operation OrdinaryHasMetadata is called with ECMAScript language value _MetadataKey_, Object _O_, and property key _P_, the following steps are taken:
139 |When the [[HasOwnMetadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_ and property key _P_, the following steps are taken:
153 |When the abstract operation OrdinaryHasOwnMetadata is called with ECMAScript language value _MetadataKey_, Object _O_, and property key _P_, the following steps are taken:
159 |When the [[GetMatadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_ and property key _P_, the following steps are taken:
171 |When the abstract operation OrdinaryGetMetadata is called with ECMAScript language value _MetadataKey_, Object _O_, and property key _P_, the following steps are taken:
177 |When the [[GetOwnMetadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_ and property key _P_, the following steps are taken:
191 |When the abstract operation OrdinaryGetOwnMetadata is called with ECMAScript language value _MetadataKey_, Object _O_, and property key _P_, the following steps are taken:
197 |When the [[DefineOwnMetadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_, ECMAScript language value _MetadataValue_, and property key _P_, the following steps are taken:
209 |When the abstract operation OrdinaryDefineOwnProperty is called with ECMAScript language value _MetadataKey_, ECMAScript language value _MetadataValue_, Object _O_, and property key _P_, the following steps are taken:
215 |When the [[MetadataKeys]] internal method of _O_ is called with property key _P_ the following steps are taken:
226 |When the abstract operation OrdinaryMetadataKeys is called with Object _O_ and property key _P_ the following steps are taken:
232 |When the [[OwnMetadataKeys]] internal method of _O_ is called with property key _P_ the following steps are taken:
270 |When the abstract operation OrdinaryOwnMetadataKeys is called with Object _O_ and property key _P_ the following steps are taken:
276 |When the [[DeleteMetadata]] internal method of _O_ is called with ECMAScript language value _MetadataKey_ and property key _P_ the following steps are taken:
302 |This section contains amendments to the Reflect object.
317 |A metadata decorator function is an anonymous built-in function that has [[MetadataKey]] and [[MetadataValue]] internal slots.
320 |When a metadata decorator function _F_ is called with arguments _target_ and _key_, the following steps are taken:
321 |When the `metadata` function is called with arguments _metadataKey_ and _metadataValue_, the following steps are taken:
336 |When the `defineMetadata` function is called with arguments _metadataKey_, _metadataValue_, _target_, and _propertyKey_, the following steps are taken:
347 |When the `hasMetadata` function is called with arguments _metadataKey_, _target_, and _propertyKey_, the following steps are taken:
356 |When the `hasOwnMetadata` function is called with arguments _metadataKey_, _target_, and _propertyKey_, the following steps are taken:
365 |When the `getMetadata` function is called with arguments _metadataKey_, _target_, and _propertyKey_, the following steps are taken:
374 |When the `getOwnMetadata` function is called with arguments _metadataKey_, _target_, and _propertyKey_, the following steps are taken:
383 |When the `getMetadataKeys` function is called with arguments _target_ and _propertyKey_, the following steps are taken:
392 |When the `getOwnMetadataKeys` function is called with arguments _target_ and _propertyKey_, the following steps are taken:
401 |When the `deleteMetadata` function is called with arguments _metadataKey_, _target_, and _propertyKey_, the following steps are taken:
410 |