lazy underscore kata

gistfile1.js

var generators = {
    range: function *rangeGenerator(start, end, step) {
        for(var i = start; i < end; i += step) {
            console.log('generating', i);
            yield i;
        }
    },
    take: function *takeGenerator(iter, n) {
        for(var i = 0; i < n; i += 1) {
            yield iter.next().value;
        }
    },
    filter: function *filterGenerator(iter, cb) {
        for(var item of iter) {
            if(cb(item)) {
                yield item;
            }
        }
    }
}

var functions = {
    range: function range(start, end, step) {
        var it = generators.range(start, end, step);
        var ret = Object.create(functions);
        ret.value = it;
        return ret;
    },
    take: function take(n) {
        var it = generators.take(this.value, n)
        var ret = Object.create(functions);
        ret.value = it;
        return ret;
    },
    filter: function filter(cb) {
        var it = generators.filter(this.value, cb)
        var ret = Object.create(functions);
        ret.value = it;
        return ret;
    }
}

var a = functions.range(0, 10, 1)
            .filter((number) => number % 2 === 0)
            .take(2)
            .value;

for(var el of a) {
    console.log('result', el);
}