AgentEpsilon/decko

:dash: The 3 most useful ES7 decorators: bind, debounce and memoize

decko

This is a fork of developit's decko that renames the incorrectly named "debounce" to "throttle", and adds an actual "debounce".

A concise implementation of the three four most useful decorators:

• @bind: make the value of this constant within a method
• @throttle: throttle calls to a method
• @debounce: debounce calls to a method
• @memoize: cache return values based on arguments

Decorators help simplify code by replacing the noise of common patterns with declarative annotations. Conversely, decorators can also be overused and create obscurity. Decko establishes 3 4 standard decorators that are immediately recognizable, so you can avoid creating decorators in your own codebase.

💡 Tip: decko is particularly well-suited to Preact Classful Components.

💫 Note:

• For Babel 6+, be sure to install babel-plugin-transform-decorators-legacy.
• For Typescript, be sure to enable {"experimentalDecorators": true} in your tsconfig.json.

Installation

Available on npm:

npm i -S @agentepsilon/decko

Usage

Each decorator method is available as a named import.

import { bind, memoize, throttle, debounce } from '@agentepsilon/decko';

@bind

class Example {
	@bind
	foo() {
		// the value of `this` is always the object from which foo() was referenced.
		return this;
	}
}

let e = new Example();
assert.equal(e.foo.call(null), e);

@memoize

Cache values returned from the decorated function. Uses the first argument as a cache key. Cache keys are always converted to strings.

Options:

caseSensitive: false - Makes cache keys case-insensitive

cache: {} - Presupply cache storage, for seeding or sharing entries

class Example {
	@memoize
	expensive(key) {
		let start = Date.now();
		while (Date.now()-start < 500) key++;
		return key;
	}
}

let e = new Example();

// this takes 500ms
let one = e.expensive(1);

// this takes 0ms
let two = e.expensive(1);

// this takes 500ms
let three = e.expensive(2);

@throttle

Throttle calls to the decorated function. To throttle means "call this at most once per N ms". All outward function calls get collated into a single inward call, and only the latest (most recent) arguments as passed on to the throttled function.

Options:

delay: 0 - The number of milliseconds to buffer calls for.

class Example {
	@throttle
	foo() {
		return this;
	}
}

let e = new Example();

// this will only call foo() once:
for (let i=1000; i--) e.foo();

@debounce

Debounce calls to the decorated function. To debounce means "call this only after it has not been called for N ms". All outward function calls clear any currently queued calls, then schedule a new call, effectively delaying the call further. As in @throttle, only the most recent arguments are passed on.

Options:

delay: 0 - The number of milliseconds to wait for repeat calls for.

class Example {
	@debounce
	foo() {
		return this;
	}
}
``

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License
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MIT