once 
Creates a function that will only execute once. Subsequent calls return the result of the first invocation.
Usage 
ts
import { once } from 'rattail'
const fn = once(() => 'initialized')
fn() // return 'initialized'
fn() // return 'initialized'Arguments 
| Arg | Type | Defaults | 
|---|---|---|
fn | Function | 
Return 
| Type | 
|---|
Function |