What is memoize-one?
The memoize-one package is a simple and lightweight memoization library designed for memoizing the result of a function based on the latest arguments. It only remembers the latest arguments and result, and it will only recompute the result when the arguments change. This can be particularly useful for optimizing performance in scenarios where expensive function calls are frequently made with the same arguments.
What are memoize-one's main functionalities?
Simple memoization of functions
This feature allows you to create a memoized version of a function that caches the result based on the latest set of arguments it was called with. If the function is called again with the same arguments, the cached result is returned instead of recomputing.
const memoizeOne = require('memoize-one');
const add = (a, b) => a + b;
const memoizedAdd = memoizeOne(add);
console.log(memoizedAdd(1, 2)); // 3
console.log(memoizedAdd(1, 2)); // 3, cached result
console.log(memoizedAdd(2, 2)); // 4, recomputed because arguments changed
Custom equality function
This feature allows you to provide a custom function to compare the equality of arguments. This is useful when you need to memoize a function that takes complex arguments like objects or arrays and the default shallow comparison is not sufficient.
const memoizeOne = require('memoize-one');
const isEqual = (newArgs, lastArgs) => JSON.stringify(newArgs) === JSON.stringify(lastArgs);
const complexFunction = (obj) => {/* complex operation */};
const memoizedComplexFunction = memoizeOne(complexFunction, isEqual);
Other packages similar to memoize-one
lodash.memoize
Lodash provides a memoize function that can cache the result of function calls based on the arguments passed. It allows for custom cache implementations and is part of the larger Lodash utility library, which provides a wide range of functions for manipulating and traversing data.
fast-memoize
Fast-memoize is a high-performance memoization library that claims to be the fastest possible memoization library in JavaScript. It supports multiple argument memoization and provides various options for cache creation, argument serialization, and strategy selection.
reselect
Reselect is a selector library for Redux that uses memoization to efficiently compute derived data from the Redux store. It is specifically designed for use with Redux and allows for creating memoized selector functions that can compute derived data, optimizing performance for Redux applications.
memoizeOne
A memoization library which only remembers the latest invocation
Rationale
Cache invalidation is hard:
There are only two hard things in Computer Science: cache invalidation and naming things.
Phil Karlton
So keep things simple and just use a cache size of one.
Unlike other memoization libraries, memoizeOne
only remembers the latest arguments and result. No need to worry about cache busting mechanisms such as maxAge
, maxSize
, exclusions
and so on which can be prone to memory leaks. memoizeOne
simply remembers the last arguments, and if the function is next called with the same arguments then it returns the previous result.
Usage
Standard usage
import memoizeOne from 'memoize-one';
const add = (a, b) => a + b;
const memoizedAdd = memoizeOne(add);
memoizedAdd(1, 2);
memoizedAdd(1, 2);
memoizedAdd(2, 3);
memoizedAdd(2, 3);
memoizedAdd(1, 2);
Play with this example
Custom equality function
You can also pass in a custom function for checking the equality of two items.
import memoizeOne from 'memoize-one';
import deepEqual from 'lodash.isEqual';
const identity = x => x;
const defaultMemoization = memoizeOne(identity);
const customMemoization = memoizeOne(identity, deepEqual);
const result1 = defaultMemoization({foo: 'bar'});
const result2 = defaultMemoization({foo: 'bar'});
result1 === result2
const result3 = customMemoization({foo: 'bar'});
const result4 = customMemoization({foo: 'bar'});
result3 === result4
Play with this example
Equality function type signature
Here is the expected flow type signature for a custom equality function:
type EqualityFn = (a: any, b: any) => boolean;
Installation
yarn add memoize-one
npm install memoize-one --save
Module usage
ES6 module
import memoizeOne from 'memoize-one';
CommonJS
If you are in a CommonJS environment (eg Node), then you will need to add .default
to your import:
const memoizeOne = require('memoize-one').default;
this
memoizeOne correctly respects this
control
This library takes special care to maintain, and allow control over the the this
context for both the original function being memoized as well as the returned memoized function. Both the original function and the memoized function's this
context respect all the this
controlling techniques:
- new bindings (
new
) - explicit binding (
call
, apply
, bind
); - implicit binding (call site:
obj.foo()
); - default binding (
window
or undefined
in strict mode
); - fat arrow binding (binding to lexical
this
) - ignored this (pass
null
as this
to explicit binding)
Changes to this
is considered an argument change
Changes to the running context (this
) of a function can result in the function returning a different value even though its arguments have stayed the same:
function getA() {
return this.a;
}
const temp1 = {
a: 20,
};
const temp2 = {
a: 30,
}
getA.call(temp1);
getA.call(temp2);
Therefore, in order to prevent against unexpected results, memoizeOne
takes into account the current execution context (this
) of the memoized function. If this
is different to the previous invocation then it is considered a change in argument. further discussion.
Generally this will be of no impact if you are not explicity controlling the this
context of functions you want to memoize with explicit binding or implicit binding. memoizeOne
will detect when you are manipulating this
and will then consider the this
context as an argument. If this
changes, it will re-execute the original function even if the arguments have not changed.
Performance :rocket:
Tiny
memoizeOne
is super lightweight at 457 bytes
minified and 299 bytes
gzipped. (1kb
= 1000 bytes
)
Extremely fast
memoizeOne
performs better or on par with than other popular memoization libraries for the purpose of remembering the latest invocation.
Results
The comparisions are not exhaustive and are primiarly to show that memoizeOne
accomplishes remembering the latest invocation really fast. The benchmarks do not take into account the differences in feature sets, library sizes, parse time, and so on.
Code health :thumbsup: