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<h1 class="page-title">memoize.js</h1>
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<pre class="prettyprint source linenums"><code>import setImmediate from './internal/setImmediate.js'
import initialParams from './internal/initialParams.js'
import wrapAsync from './internal/wrapAsync.js'
/**
* Caches the results of an async function. When creating a hash to store
* function results against, the callback is omitted from the hash and an
* optional hash function can be used.
*
* **Note: if the async function errs, the result will not be cached and
* subsequent calls will call the wrapped function.**
*
* If no hash function is specified, the first argument is used as a hash key,
* which may work reasonably if it is a string or a data type that converts to a
* distinct string. Note that objects and arrays will not behave reasonably.
* Neither will cases where the other arguments are significant. In such cases,
* specify your own hash function.
*
* The cache of results is exposed as the `memo` property of the function
* returned by `memoize`.
*
* @name memoize
* @static
* @memberOf module:Utils
* @method
* @category Util
* @param {AsyncFunction} fn - The async function to proxy and cache results from.
* @param {Function} hasher - An optional function for generating a custom hash
* for storing results. It has all the arguments applied to it apart from the
* callback, and must be synchronous.
* @returns {AsyncFunction} a memoized version of `fn`
* @example
*
* var slow_fn = function(name, callback) {
* // do something
* callback(null, result);
* };
* var fn = async.memoize(slow_fn);
*
* // fn can now be used as if it were slow_fn
* fn('some name', function() {
* // callback
* });
*/
export default function memoize(fn, hasher = v => v) {
var memo = Object.create(null);
var queues = Object.create(null);
var _fn = wrapAsync(fn);
var memoized = initialParams((args, callback) => {
var key = hasher(...args);
if (key in memo) {
setImmediate(() => callback(null, ...memo[key]));
} else if (key in queues) {
queues[key].push(callback);
} else {
queues[key] = [callback];
_fn(...args, (err, ...resultArgs) => {
// #1465 don't memoize if an error occurred
if (!err) {
memo[key] = resultArgs;
}
var q = queues[key];
delete queues[key];
for (var i = 0, l = q.length; i < l; i++) {
q[i](err, ...resultArgs);
}
});
}
});
memoized.memo = memo;
memoized.unmemoized = fn;
return memoized;
}
</code></pre>
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<h3>Methods:</h3><ul class="nav methods"><li class="toc-header"><a href="docs.html#collections">Collections</a></li><li data-type="method" class="toc-method"><a href="docs.html#concat">concat</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatLimit">concatLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#concatSeries">concatSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#detect">detect</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectLimit">detectLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#detectSeries">detectSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#each">each</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachLimit">eachLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOf">eachOf</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOfLimit">eachOfLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachOfSeries">eachOfSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#eachSeries">eachSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#every">every</a></li><li data-type="method" class="toc-method"><a href="docs.html#everyLimit">everyLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#everySeries">everySeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#filter">filter</a></li><li data-type="method" class="toc-method"><a href="docs.html#filterLimit">filterLimit</a></li><li data-type="method" class="toc-method"><a href="docs.html#filterSeries">filterSeries</a></li><li data-type="method" class="toc-method"><a href="docs.html#groupBy">groupBy</a></li><li data-type="method" class="toc-method"><a href="docs.html#groupByLimit">groupByLimit</a></li><li data-type="method" 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