Add setInterval and clearInterval

I noticed that setInterval is not a thing in windowjs, so I decided to write my own implementation:

function* getIntervalIdgen() {
    var i = 0;
    yield i++;
}

const intervalIdGenerator = getIntervalIdgen();

function getId() {
    return intervalIdGenerator.next.value;
}

{
    var g;
    if (typeof window !== "undefined") {
        g = window;
    } else if (typeof global !== "undefined") {
        g = global;
    } else if (typeof self !== "undefined") {
        g = self;
    } else {
        g = this;
    }

    g.setInterval = function (callback, timer) {
        let id = getId();

        g.intervalState.intervals.push({
            callback,
            timer,
            timeDelta: Date.now(),
            id,
        });

        return id;
    };
    g.clearInterval = function (id) {
        g.intervalState.intervals = g.intervalState.intervals.filter(function (
            item
        ) {
            return item.id != id;
        });
    };
    g.intervalState = {};
    g.intervalState.intervals = [];

    function fireIntervals() {
        requestAnimationFrame(fireIntervals);

        for (const interval of g.intervalState.intervals) {
            if (Date.now() - interval.timeDelta >= interval.timer) {
                interval.callback();
                interval.timeDelta = Date.now();
            }
        }
    }
    requestAnimationFrame(fireIntervals);
}

Would be nice if I could contribute that to the repo, but I don't want to mess with c.