@babel/plugin-proposal-function-bind
Detail
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
const box = { weight: 2, getWeight() { return this.weight; }, }; const { getWeight } = box; console.log(box.getWeight()); // prints '2' const bigBox = { weight: 10 }; console.log(bigBox::getWeight()); // prints '10' // Can be chained: function add(val) { return this + val; } console.log(bigBox::getWeight()::add(5)); // prints '15'
Using with document.querySelectorAll
It can be very handy when used with document.querySelectorAll
:
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:
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:
$(".some-link").on("click", ::view.reset); // is equivalent to: $(".some-link").on("click", view.reset.bind(view));
Installation
npm install --save-dev @babel/plugin-proposal-function-bind
Usage
With a configuration file (Recommended)
{ "plugins": ["@babel/plugin-proposal-function-bind"] }
Via CLI
babel --plugins @babel/plugin-proposal-function-bind script.js
Via Node API
require("@babel/core").transformSync("code", { plugins: ["@babel/plugin-proposal-function-bind"], });