Compile the new function bind operator `::` to ES5.
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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)
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'
document.querySelectorAllIt 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);
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));
npm install --save-dev babel-plugin-transform-function-bind
.babelrc (Recommended).babelrc
{
"plugins": ["transform-function-bind"]
}
babel --plugins transform-function-bind script.js
require("babel-core").transform("code", {
plugins: ["transform-function-bind"]
});