32 lines
806 B
TypeScript
32 lines
806 B
TypeScript
/**
|
|
Define a [lazily evaluated](https://en.wikipedia.org/wiki/Lazy_evaluation) property on an object.
|
|
|
|
@param object - Object to add the property to.
|
|
@param propertyName - Name of the property to add.
|
|
@param valueGetter - Called the first time `propertyName` is accessed.
|
|
|
|
@example
|
|
```
|
|
import defineLazyProperty from 'define-lazy-prop';
|
|
|
|
const unicorn = {
|
|
// …
|
|
};
|
|
|
|
defineLazyProperty(unicorn, 'rainbow', () => expensiveComputation());
|
|
|
|
app.on('user-action', () => {
|
|
doSomething(unicorn.rainbow);
|
|
});
|
|
```
|
|
*/
|
|
export default function defineLazyProperty<
|
|
ObjectType extends Record<string, any>,
|
|
PropertyNameType extends string,
|
|
PropertyValueType
|
|
>(
|
|
object: ObjectType,
|
|
propertyName: PropertyNameType,
|
|
valueGetter: () => PropertyValueType
|
|
): ObjectType & {[K in PropertyNameType]: PropertyValueType};
|