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