Is the default lodash memoize function a danger for memory leaks?

Question

I want to use memoize but I have a concern that the cache will grow indefinitely until sad times occur.

I couldn't find anything via google/stackoverflow searches.

P.S. I am using lodash v4.

Answer 1

Lodash retains all the memoized data unless you specify a different Cache type.

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The default cache is lodash's MapCache:
https://github.com/lodash/lodash/blob/4.14.0/lodash.js#L1968

The memoized values are stored in different data structures depending on whether the key is suitable for hashing (and whether or not ES6 Map is available in the environment):
https://github.com/lodash/lodash/blob/4.14.0/lodash.js#L1987 https://github.com/lodash/lodash/blob/4.14.0/lodash.js#L5561

If you look at the "set" methods of all of these data structures, you'll notice there is no provision for anything like LRU etc:
Hash#set: https://github.com/lodash/lodash/blob/4.14.0/lodash.js#L1832
ListCache#set: https://github.com/lodash/lodash/blob/4.14.0/lodash.js#L1940
Map#set: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/set

Answer 2

Short answer is no.

When you use a memoize function you accept a contract that:

1. The function will only be invoked once with a given argument
2. The cache stays there as long as it's necessary to guarantee the #1 (forever)

So only the implementation that keeps data forever can comply with the requirements.

What is very often confused - is a "memory leak" thing with just "inefficient" use of memory.

In this case - if it is a problem for you, then it is your responsibility to re-create a memoized function when it's good for your algorithm. Since it is only you that knows when it is safe to do so, and it cannot be done automatically.