segal-decorators

Segal Decorators

Bunch of useful decorators

Table of contents

• Installation
• Contributing
• Changelog
• Decorators
  • Memoize
  • Time Memoize
  • Lru Memoize
  • Debounce
  • Throttle
  • Async Retry
  • Once

Installation

Use npm to install the package

$ npm install segal-decorators --save 

Decorators

Memoize

Memoize the function by using the cached result. If hashFn is passed it is used to compute the hash key. default hash function is using JSON.stringify on the original function arguments.

Declaration

function Memoize(hashFn?: (...args: any[]) => string)

Usage

import { Memoize } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @Memoize()
  count(...args: any[]) {
    return ++this.counter;
  }
}

console.log(test.count(1)); // Outputs: 1
console.log(test.count(2)); // Outputs: 2
console.log(test.count(1)); // Outputs: 1
console.log(test.count(1, 2)); // Outputs: 3
console.log(test.count(2)); // Outputs: 2

Time Memoize

Time memoization, similar to Memoize, requires an additional parameter timeoutMs to determine the amount of time in milliseconds to cache the result.

Declaration

function TimeMemoize(timeoutMs: number, hashFn?: (...args: any[]) => string)

Usage

import { TimeMemoize } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @TimeMemoize(2000)
  count(...args: any[]) {
    return ++this.counter;
  }
}

console.log(test.count(1)); // Outputs: 1
console.log(test.count(2)); // Outputs: 2
console.log(test.count(1)); // Outputs: 1
console.log(test.count(2)); // Outputs: 2

setTimeout(() => {
  console.log(test.count(1)); // Outputs: 3
  console.log(test.count(2)); // Outputs: 4
}, 3000);

Lru Memoize

Least-recently-used memoization, similar to Memoize, requires an additional parameter maxRecords of the number of records to keep in cache.

Declaration

function LruMemoize(maxRecords: number, hashFn?: (...args: any[]) => string)

Usage

import { LruMemoize } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @LruMemoize(2)
  count(...args: any[]) {
    return ++this.counter;
  }
}

console.log(test.count(1)); // State of LRU Cache=[1], Outputs: 1 
console.log(test.count(2)); // State of LRU Cache=[2, 1], Outputs: 2
console.log(test.count(3)); // State of LRU Cache=[3, 2], Outputs: 3
console.log(test.count(2)); // State of LRU Cache=[2, 3], Outputs: 2
console.log(test.count(1)); // State of LRU Cache=[1, 2], Outputs: 4

Debounce

Postpone its execution until after timeMs have elapsed since the last time it was invoked.

Declaration

function Debounce(timeMs: number)

Usage

import { Debounce } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @Debounce(2000)
  call() {
    return ++this.counter;
  }
}

console.log(test.call()); // Does not output anything since it's called again with-in the 2 second time-frame.
console.log(test.call()); // Outputs: 1 (AFTER 2 SECONDS)

setTimeout(() => {
  console.log(test.call()); // Outputs: 1 (AFTER ADDITIONAL 2 SECONDS)
}, 3000)

Throttle

When invoked repeatedly, will only call the original function at most once per every timeMs.

Declaration

function Throttle(timeMs: number)

Usage

import { Throttle } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @Throttle(2000)
  call() {
    return ++this.counter;
  }
}

console.log(test.call()); // Outputs: 1
console.log(test.call()); // Does not output anything since it's called again with-in the 2 second time-frame.

setTimeout(() => {
  console.log(test.call());
  // Outputs: 1 
}, 3000)

Async Retry

In-case an exception has been thrown, it will retry the action up to retries amount of times with a restMs delay between attempts.

Declaration

function AsyncRetry(retries: number, restMs: number = 100)

Usage

import { AsyncRetry } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @AsyncRetry(2)
  doSomething() {
    return requestServerSomething()
  }
}

// in-case of a failure will try twice before throwing an exception
test.doSomething().then((response) => {
  // Reach here if succeed in one of the 2 attempts
}).catch(() => {
  // Reach here if failed after 2 attempts
})

Once

Called exactly once. Repeated calls will have no effect, returning the value from the first call.

Declaration

function Once()

Usage

import { Once } from 'segal-decorators';

class Foo {
  counter = 0;
  
  @Once()
  count(...args: string[]) {
    return ++this.counter;
  }
}

console.log(test.count()); // Outputs: 1
console.log(test.count()); // Outputs: 1
console.log(test.count(1)); // Outputs: 1
console.log(test.count(1, 2)); // Outputs: 1