2024-05-06 20:40:05 +00:00
|
|
|
---
|
2024-10-30 17:34:11 +00:00
|
|
|
date: 2020-07-02
|
2024-05-06 20:40:05 +00:00
|
|
|
id: 8659a753-2c0d-46cb-afdc-095e318aabff
|
|
|
|
|
title: Closure in JavaScript
|
|
|
|
|
---
|
|
|
|
|
|
|
|
|
|
Local bindings are created anew for every call, and different calls
|
|
|
|
|
can't affect on another calls local bindings.
|
|
|
|
|
|
|
|
|
|
``` javascript
|
|
|
|
|
function wrapValue(n) {
|
|
|
|
|
let local = n;
|
|
|
|
|
return () => local;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
let wrap1 = wrapValue(1);
|
|
|
|
|
let wrap2 = wrapValue(2);
|
|
|
|
|
console.log(wrap1());
|
|
|
|
|
console.log(wrap2());
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
A function that references bindings from local scopes around it is
|
|
|
|
|
called a closure. This behavior not only frees you from having to worry
|
|
|
|
|
about lifetimes of bindings but also makes it possible to use function
|
|
|
|
|
values in some creative ways.
|
|
|
|
|
|
|
|
|
|
``` javascript
|
|
|
|
|
function multiplier(factor) {
|
|
|
|
|
return number => number * factor;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
let twice = multiplier(2);
|
|
|
|
|
|
|
|
|
|
console.log(twice(5));
|
|
|
|
|
```
|
