69 lines
1.6 KiB
TypeScript
69 lines
1.6 KiB
TypeScript
"use client";
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import { useEffect, useRef, useState } from "react";
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type Props = {
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to: number;
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prefix?: string;
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suffix?: string;
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decimals?: number;
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duration?: number;
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};
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/**
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* Count-up that fires once when scrolled into view. Renders the final
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* value immediately under reduced motion (and as SSR fallback) so the
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* real number is always present for assistive tech and no-JS.
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*/
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export default function CountUp({
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to,
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prefix = "",
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suffix = "",
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decimals = 0,
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duration = 1600,
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}: Props) {
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const ref = useRef<HTMLSpanElement>(null);
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const [val, setVal] = useState(to);
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const done = useRef(false);
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useEffect(() => {
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const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
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if (reduce) {
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setVal(to);
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return;
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}
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setVal(0);
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const node = ref.current;
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if (!node) return;
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const io = new IntersectionObserver(
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([e]) => {
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if (!e.isIntersecting || done.current) return;
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done.current = true;
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const start = performance.now();
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const tick = (now: number) => {
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const p = Math.min((now - start) / duration, 1);
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const eased = 1 - Math.pow(1 - p, 3);
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setVal(to * eased);
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if (p < 1) requestAnimationFrame(tick);
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};
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requestAnimationFrame(tick);
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io.disconnect();
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},
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{ threshold: 0.4 }
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);
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io.observe(node);
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return () => io.disconnect();
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}, [to, duration]);
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return (
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<span ref={ref}>
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{prefix}
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{val.toLocaleString("en-US", {
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minimumFractionDigits: decimals,
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maximumFractionDigits: decimals,
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})}
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{suffix}
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</span>
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);
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}
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