just-animate/lib.es2015/lib/core/timeloop.js

_Making Animation Simple_

import { _ } from '../utils/constants';
import { push, includes, remove } from '../utils/lists';
import { dispatch } from '../store';
import { TICK } from '../actions';
const raf = requestAnimationFrame;
const caf = cancelAnimationFrame;
const now = () => performance.now();
const active = [];
const deltas = {};
let lastHandle = _;
let lastTime = _;
function cancel() {
    caf(lastHandle);
    lastHandle = lastTime = _;
}
function update() {
    const len = active.length;
    lastTime = lastTime || now();
    if (!len) {
        cancel();
        return;
    }
    const thisTime = now();
    const delta = thisTime - lastTime;
    lastTime = thisTime;
    lastHandle = raf(update);
    for (let i = len - 1; i > -1; i--) {
        const activeId = active[i];
        deltas[activeId] += delta;
        dispatch(TICK, activeId, delta);
    }
}
export function loopOn(id) {
    if (!includes(active, id)) {
        deltas[id] = 0;
        push(active, id);
    }
    if (!lastHandle) {
        lastHandle = raf(update);
    }
}
export function loopOff(id) {
    if (remove(active, id)) {
        delete deltas[id];
    }
    if (!active.length) {
        cancel();
    }
}