@babel/plugin-proposal-function-bind
Detail
JavaScript
obj::func;
// is equivalent to:
func.bind(obj)
::obj.func;
// is equivalent to:
obj.func.bind(obj);
obj::func(val);
// is equivalent to:
func
.call(obj, val)
::obj.func(val);
// is equivalent to:
obj.func.call(obj, val);
Example
Basic
JavaScript
const box ={
weight:2,
getWeight(){
returnthis.weight;
},
};
const{ getWeight }= box;
console.log(box.getWeight());// prints '2'
const bigBox ={weight:10};
console.log(bigBox::getWeight());// prints '10'
// Can be chained:
functionadd(val){
returnthis+ val;
}
console.log(bigBox::getWeight()::add(5));// prints '15'
Using with document.querySelectorAll
It can be very handy when used with document.querySelectorAll:
JavaScript
const{ map, filter }=Array.prototype;
let sslUrls =document
.querySelectorAll("a")
::map(node=> node.href)
::filter(href=> href.substring(0,5)==="https");
console.log(sslUrls);
document.querySelectorAll returns a NodeList element which is not a plain array, so you normally can't use the map function on it, and have to use it this way: Array.prototype.map.call(document.querySelectorAll(...), node => { ... }). The above code using the :: will work because it is equivalent to:
JavaScript
const{ map, filter }=Array.prototype;
let sslUrls =document.querySelectorAll("a");
sslUrls = map.call(sslUrls,node=> node.href);
sslUrls = filter.call(sslUrls,href=> href.substring(0,5)==="https");
console.log(sslUrls);
Auto self binding
When nothing is specified before the :: operator, the function is bound to its object:
JavaScript
$(".some-link").on("click",::view.reset);
// is equivalent to:
$(".some-link").on("click", view.reset.bind(view));
Installation
- npm
- Yarn
- pnpm
- Bun
npm install --save-dev @babel/plugin-proposal-function-bind
yarn add --dev @babel/plugin-proposal-function-bind
pnpm add --save-dev @babel/plugin-proposal-function-bind
bun add --dev @babel/plugin-proposal-function-bind
Usage
With a configuration file (Recommended)
babel.config.json
{
"plugins":["@babel/plugin-proposal-function-bind"]
}
Via CLI
Shell
babel --plugins @babel/plugin-proposal-function-bind script.js
Via Node API
JavaScript
require("@babel/core").transformSync("code",{
plugins:["@babel/plugin-proposal-function-bind"],
});