@byte-this/funscript
v1.0.42
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A typescript API which facilitates functional programming.
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Funscript - Functional Typescript
For details + info on how to use: https://bytethisstore.com/articles/pg/funscript
This library facilitates functional programming practices by offering:
- recursive object cloning
- recursive object locking
- asynchronous versions of array functions
- compose utility to pipe multiple functions into one
- deep equality checking
These will aid in creating and working with immutable objects.
Install
Library with typescript definitions available as npm package.
npm install @byte-this/funscript
Clone
The Clone
function is straightforward: it recursively clones an object and returns the new object:
const newObj = Clone(oldObject);
console.log(oldObject === newObj); //false
If the object has its own clone
method, this function will utilize it. Otherwise, it will do a default recursive clone.
Lock
The Lock
function clones an object and recursively freezes all properties on that clone, preventing any further mutation:
const oldObj = {
property: {
a: true,
b: false,
},
};
const newObj = Lock(oldObject);
console.log(oldObject === newObj); //fales
try {
newObj.property.a = false;
//if 'strict mode' is not enabled, no error will be thrown
//but the object field will not be updated
} catch (err) {
//an error will be thrown if you have 'strict mode' enabled
//which I recommend you should
}
FunAr
FunAr: functional asynchronous array, provides asynchronous versions of the common functional array methods in sequential and parallel flavors:
- Sequential
- map
- filter
- reduce
- find
- forEach (not technically functional but included for completeness)
- Parallel
- map
- filter
- forEach (not technically functional but included for completeness)
The sequential methods invoke the callback for each item one after another. The parallel methods invoke the callback for each item simultaneously.
//the methods have the same signature as the regular version, except the input array is added as the first argument
const reduced = await FunAr.async.seq.reduce(inputArray, reduceFunction, initialValue);
const mapped = await FunAr.async.parallel.map(inputArray, (item, index) => /*..async*/ return mapped);
Compose
Compose multiple functions and assign it to a single variable or execute immediately:
const compositeFunction = Compose(fOne, fTwo, fThree, fFour);
const result = compositeFunction(initialParam, otherParm); //first input function can accept more than one parameter
//async version
const compositeAsyncFunction = ComposeAsync(fOneAsync, fTwoAsync, fThreeAsync);
const result = await compositeAsyncFunction(input);
//dynamic composition
const dynamicComposition = Compose(...arrayOfFunctions);
const result = dynamicComposition();
Equals
Check if two objects are equal. The following are considered to be equal:
- Two primitives with the same value
- Two objects with the same object reference
- Two dates with the same datetime
- Two arrays with the same contents in the same order and the contents are Equal
- Two objects with the same keys and value pairs are Equal
Equals(true, true); //true
Memoization
Memoization is a technique where the response of a function is stored so that future calls with the same parameters receive the cached response instead of executing from scratch. Below is a basic example:
const memoized = Memoize(exensiveFunc);
const resultOne = memoized(funcParamOne, funcParamTwo); //this first call runs the expensiveFunc
const resultTwo = memoized(funcParamOne, funcParamTwo); //this second call does not run expensiveFunc, it returns the result from the first execution
const resultThree = memoized(newFuncParamOne, newFuncParamTwo); //this runs expensiveFunc again because the arguments are different than the first call
With the default parameters, cached values are stored indefinitely. It is also possible to configure an expiration time:
const memoized = Memoize(exensiveFunc, {
cacheExpiration: {
evaluate: () => numMs, //a function which returns a number in milliseconds
type: "relative" | "absolute", //specificy if the timestamp is relative to now or absolute
},
});
When the cache item expires, the memoized fnction will run the real function the next time it is invoked.
Async version:
const memoized = MemoizeAsync(expensiveFunc);
Decorator version:
class TestClass {
@MemoizeMethod() //this can take the same options as the normal method call
expensiveFuncOne() {
/** some expensive operation */
}
@MemoizeAsyncMethod()
async expensiveFuncTwo() {
/** some async expensive operation */
}
}
Collect Pending Method Invocations
Wrap an async function so it collects multiple invocations and waits for the response of the first call instead of calling the function multiple times.
const asyncFunc = async () => { /** some async function, such as network call */ return response; };
const wrappedFunc = CollectPendingInvocations(asyncFunc);
Promise.all([
wrappedFunc(param),
wrappedFunc(param),
wrappedFunc(param)
]).then(data => console.log(data)); //logs array of three responses, but original method was only called once
There is also a decorator for class methods:
class TestClass {
@CollectPendingMethodInvocations
asyncOperation() {
/** some async operation */
return response;
}
}
Other Array Functions
The following functions exist on FunAr and can have custom equality comparators passed in when applicable
- uniqueValues: get the unique values of an array
- subset: get a subset of an array from the start to end index
- isSubsetOf: check if an array is a subset of another array
- isSupersetOf: check if an array is a superset of another array
- intersection: get the intersection (common values) of two arrays
- intersects: check if two arrays have any intersection