126 lines
2.8 KiB
Markdown
126 lines
2.8 KiB
Markdown
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<!--
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@license Apache-2.0
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Copyright (c) 2019 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# Define Memoized Property
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> [Define][mdn-define-property] a memoized object property.
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<section class="usage">
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## Usage
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```javascript
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var defineMemoizedProperty = require( '@stdlib/utils/define-memoized-property' );
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```
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#### defineMemoizedProperty( obj, prop, descriptor )
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[Defines][mdn-define-property] a memoized object property.
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```javascript
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var obj = {};
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function foo() {
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return 'bar';
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}
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defineMemoizedProperty( obj, 'foo', {
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'configurable': false,
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'enumerable': true,
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'writable': false,
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'value': foo
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});
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var v = obj.foo;
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// returns 'bar'
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```
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A property `descriptor` has the following required properties:
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- **value**: synchronous function whose return value will be memoized and set as the property value.
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A property `descriptor` has the following optional properties:
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- **configurable**: `boolean` indicating if property descriptor can be changed and if the property can be deleted from the provided object. Default: `false`.
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- **enumerable**: `boolean` indicating if the property shows up when enumerating object properties. Default: `false`.
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- **writable**: `boolean` indicating if the value associated with the property can be changed with an assignment operator. Default: `false`.
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- Until deferred evaluation, an object property is **configurable**.
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var fibonacci = require( '@stdlib/math/base/special/fibonacci' );
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var defineMemoizedProperty = require( '@stdlib/utils/define-memoized-property' );
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function Foo() {
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var self;
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if ( !(this instanceof Foo) ) {
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return new Foo();
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}
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self = this;
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this.count = 0;
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defineMemoizedProperty( this, 'fibo', {
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'value': fibo
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});
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return this;
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function fibo() {
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self.count += 1;
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return fibonacci( 73 );
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}
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}
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var foo = new Foo();
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var i;
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for ( i = 0; i < 10; i++ ) {
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console.log( 'F: %d. Count: %d.', foo.fibo, foo.count );
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[mdn-define-property]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty
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</section>
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<!-- /.links -->
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