babeljs - Javascript new syntax implementation

Question

Can anyone give me a direction on how to implement python like syntax of lists array[-1] using Babel in javascript? I mean how to implement negative indexes.

Answer 1

You could go with your own proxy implementation and then use it.

const letters = ['a', 'b', 'c', 'd', 'e'];
const proxy = new Proxy(letters, {
    get(target, prop) {
        if (!isNaN(prop)) {
            prop = parseInt(prop, 10);
            if (prop < 0) {
                prop += target.length;
            }
        }
        return target[prop];
    }
});
proxy[0]; // => 'a'
proxy[-1]; // => 'e'
proxy[-2]; // => 'd'

Please refer to this article on medium explaining in detail how to do this. I do not know of another way, perhaps there is a babel plugin that could help.