ridder/dist/state.js

A straightforward game engine for simple data-driven games in JavaScript

import { resetTimer, tickTimer, timer } from "./timer.js";
const TARGET_FRAME_TIME = 1000 / 60;
const framesTimer = timer();
let last = 0;
let now = 0;
let delta = 0;
let time = 0;
let elapsed = 0;
let frames = 0;
let fps = 0;
/**
 * Set the initial time.
 */
export function setupState() {
    last = performance.now();
    now = performance.now();
}
/**
 * Update the current state of the game loop.
 */
export function updateState() {
    last = now;
    now = performance.now();
    time = now - last;
    delta = time / TARGET_FRAME_TIME;
    // If the delta time is too high, ignore the frame.
    if (time > 100) {
        return false;
    }
    frames++;
    if (tickTimer(framesTimer, 1000)) {
        fps = frames;
        frames = 0;
        resetTimer(framesTimer);
    }
    elapsed += time;
    return true;
}
/**
 * The scalar value of the time between the last frame and the current frame.
 * This value is calculated based on the desired 60 frames per second.
 *
 * Using this value will make sure that your game runs at the same speed on all frame rates.
 *
 * NOTE - Use this for physics or movement. For animations (tweens) or timers, use {@link getDeltaTime} instead.
 */
export function getDelta() {
    return delta;
}
/**
 * The time in milliseconds between the last frame and the current frame.
 *
 * NOTE - Use this for animations (tweens) or timers. For physics or movement, use {@link getDelta} instead.
 */
export function getDeltaTime() {
    return time;
}
/**
 * Get the current frames per second.
 */
export function getFramePerSecond() {
    return fps;
}
/**
 * Get the elapsed time in milliseconds since the game started.
 */
export function getElapsedTime() {
    return elapsed;
}