It'd be really useful to have variables inside methods/functions that are
initialized once, reused for subsequent calls and live as long as containing
scope i.e the function itself.
> not to be confused with `static` properties
## Use Cases
Almost every app has a function or method that needs to "preserve" some state
across multiple calls, a counter for example. Current ways out of this
situation are either closures created with IIFE's or making those variables
top-level. Both of which are ugly. I think the same could be done much more
neatly with persistent variables.
## Example
```javascript
function foo(n) {
// initialized on first call to foo, persists for subsequent calls
persist let counter = 0;
// this way JS engine won't have to recompile the pattern everytime
persist const httpRE = /^https?/;
counter++;
return n * a;
}
```
is 1:1 as
```javascript
let foo = (() => {
let counter = 0;
const httpRE = /^https?/;
return (n) => {
counter++;
return n * a;
}
})()
```
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