123 lines
2.1 KiB
JavaScript
123 lines
2.1 KiB
JavaScript
const N = 12;
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class ProgView {
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constructor(addfn) {
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this.n = null;
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this.s = null;
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this.last = 0;
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this.stored = false;
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this.first = true;
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this.loading = false;
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this.nomore = false;
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this.addelements = addfn;
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this.load();
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this.down(this.n).then(() => {
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let app = this;
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(function ev() {
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if (document.documentElement.scrollHeight < app.s) {
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setTimeout(ev, 50);
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} else {
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window.scrollTo(0, app.s);
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}
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})();
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});
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}
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get n() {
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return this.nval;
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}
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set n(sn) {
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this.nval = sn == null ? N : Number(sn);
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}
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get s() {
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return this.sval;
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}
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set s(ss) {
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this.sval = ss == null ? 0 : Number(ss);
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}
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arm() {
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window.onscroll = (ev) => {
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if ((window.innerHeight + window.scrollY + 50) >= document.body.offsetHeight) {
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this.down();
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}
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};
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}
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disarm() {
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window.onscroll = null;
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}
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store(s) {
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this.stored = true;
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this.n = this.last;
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this.s = window.scrollY;
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sessionStorage.setItem("n", this.n);
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sessionStorage.setItem("s", this.s);
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}
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load() {
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this.n = window.sessionStorage.getItem("n");
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this.s = window.sessionStorage.getItem("s");
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}
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clear() {
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sessionStorage.removeItem("n");
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sessionStorage.removeItem("s");
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}
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stopload() {
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let gif = document.querySelector("div#load > img");
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gif.remove();
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}
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startload() {
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let load = document.getElementById("load");
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let gif = document.createElement("img");
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gif.setAttribute("src", "static/load.gif");
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gif.setAttribute("class", "load");
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load.appendChild(gif);
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return true;
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}
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async down(n) {
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n = n == null ? this.n : n;
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this.disarm();
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if (!this.loading && !this.nomore) {
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this.loading = true;
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this.startload();
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await fetch(`list?o=${this.last}&n=${n}`)
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.then(response => {
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if (!response.ok) {
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throw `down(): error ${response.status}`;
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} else {
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return response.json();
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}
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})
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.then(data => {
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this.nomore = this.addelements(data, this.s);
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})
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.catch(error => {
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console.error(error);
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})
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.finally(() => {
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this.stopload();
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this.arm();
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this.loading = false;
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});
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this.last += n;
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}
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}
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addelements() {
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return true;
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}
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}
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