Transforms Iterables

iterable_transformer.js

// Here's a generic transformer helper function
const transform = (function(EMPTY) {
    const transform = function*(iterable, trasformers) {
        for (let res of iterable) {
            for (let i = 0; i < trasformers.length && res !== EMPTY; i++) {
                res = trasformers[i](res);
            };

            if (res !== EMPTY) yield res;
        }
    };

    transform.filter = (func) => (val) => (func(val) ? val : EMPTY);
    transform.map = (func) => (val) => func(val);
    return transform;
})(Symbol('Empty'));

// Heres a usage scenario of the "transform" function
const FILE_PREFIX = "file:///";

let uris = new Set([
    'file:///foo.txt',
    'http:///npmjs.com',
    'file:///bar/baz.txt'
]);

let newUris = new Set(
    transform(uris, [
        transform.filter((uri) => uri.startsWith(FILE_PREFIX)),
        transform.map((uri) => uri.substr(FILE_PREFIX.length))
    ])
);