90 lines
2.3 KiB
Markdown
90 lines
2.3 KiB
Markdown
Memoize functions results using an lru-cache.
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## Installation
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```
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npm i lru-memoizer --save
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```
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## Intro
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This module uses an [lru-cache](https://github.com/isaacs/node-lru-cache) internally to cache the results of an async function.
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The `load` function can have N parameters and the last one must be a callback. The callback should be an errback (first parameter is `err`).
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The `hash` function purpose is generate a custom hash for storing results. It has all the arguments applied to it minus the callback, and must return a synchronous string.
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The `disable` function allows you to conditionally disable the use of the cache. Useful for test environments.
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The `freeze` option (defaults to **false**) allows you to deep-freeze the result of the async function.
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The `clone` option (defaults to **false**) allows you to deep-clone the result every time is returned from the cache.
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## Usage
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```javascript
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const memoizer = require("lru-memoizer");
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const memoizedGet = memoizer({
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//defines how to load the resource when
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//it is not in the cache.
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load: function (options, callback) {
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request.get(options, callback);
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},
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//defines how to create a cache key from the params.
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hash: function (options) {
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return options.url + qs.stringify(options.qs);
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},
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//don't cache in test environment
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disable: isTestEnv(),
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//all other params for the LRU cache.
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max: 100,
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ttl: 1000 * 60,
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});
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memoizedGet(
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{
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url: "https://google.com",
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qs: { foo: 123 },
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},
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function (err, result, body) {
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//console.log(body);
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}
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);
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```
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## Synchronous lru-memoizer
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Use `memoizer.sync` to cache things that are slow to calculate, methods returning promises, or only if you don't want to use a callback and want it synchronous.
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```javascript
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const memoizer = require("lru-memoizer");
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const memoizedGet = memoizer.sync({
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//defines how to load the resource when
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//it is not in the cache.
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load: function (params) {
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return somethingHardToCompute();
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},
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//defines how to create a cache key from the params.
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hash: function (params) {
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return params.foo;
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},
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//all other params for the LRU cache.
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max: 100,
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ttl: 1000 * 60,
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});
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```
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## Similar modules
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This module is very similar to [async-cache](https://github.com/isaacs/async-cache)<sup>(deprecated)</sup>, the main difference is the `hash` function.
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## License
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MIT 2016 - José F. Romaniello
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