Package Exports

lazy-get-decorator

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Readme

Lazy Get decorator

Previously known as typescript-lazy-get-decorator.

Compatibility

Typescript - full
Spec-compliant decorator proposal - full
Babel (current proposal) - full
Babel (legacy) - full

API

/**
 * Evaluate the getter function and cache the result
 * @param {boolean} [setProto=false] Set the value on the class prototype as well. Only applies to non-static getters.
 * @param {boolean} [makeNonConfigurable=false] Set to true to make the resolved property non-configurable
 * @param {ResultSelectorFn} [resultSelector] A filter function that must return true for the value to cached
 * @return A Typescript decorator function
 */
function LazyGetter(setProto?: boolean, makeNonConfigurable?: boolean, resultSelector?: (value: any) => boolean): MethodDecorator;

Usage

import {LazyGetter} from 'lazy-get-decorator';

class AClass {

    @LazyGetter()
    get lazyNoProto(): string {
        console.log('Evaluating lazyNoProto');

        return 'lazyNoProtoValue';
    }

    @LazyGetter(true)
    get lazyWithProto(): string {
        console.log('Evaluating lazyWithProto');

        return 'lazyWithProtoValue';
    }
}

const inst1 = new AClass();

console.log('==== inst 1 ====\n');

console.log(inst1.lazyNoProto);
console.log(inst1.lazyNoProto);
console.log(inst1.lazyWithProto);
console.log(inst1.lazyWithProto);

const inst2 = new AClass();

console.log('\n\n==== inst 2 ====\n');

console.log(inst2.lazyNoProto);
console.log(inst2.lazyNoProto);
console.log(inst2.lazyWithProto);
console.log(inst2.lazyWithProto);

Output:

==== inst 1 ====

Evaluating lazyNoProto
lazyNoProtoValue
lazyNoProtoValue
Evaluating lazyWithProto
lazyWithProtoValue
lazyWithProtoValue


==== inst 2 ====

Evaluating lazyNoProto
lazyNoProtoValue
lazyNoProtoValue
lazyWithProtoValue
lazyWithProtoValue

Using the result selector

import {LazyGetter} from 'lazy-get-decorator';

class MyClass {
  public readonly someCondition = 10;
  
  @LazyGetter(false, false, (v: number) => v === 10)
  public get prop1(): number {
    // This will get cached
    return this.someCondition;
  }
  
  @LazyGetter(false, false, (v: number) => v === 1)
  public get prop2(): number {
    // This won't get cached
    return this.someCondition;
  }
}