97 # session

npm init -y
npm i koa @koa/router

const Koa = require("koa");
const Router = require("@koa/router");
const crypto = require("crypto");
const app = new Koa();
let router = new Router();
app.use(router.routes());
app.keys = ["kaimo"];
router.get("/visit", async (ctx, next) => {
    let visit = ctx.cookies.get("visit") || 0;
    visit++;
    ctx.cookies.set("visit", `${visit}`, {
        httpOnly: true,
        signed: true
    });
    ctx.body = `你当前访问次数${visit}，签名：${crypto.createHmac("sha1", "kaimo").update(`visit=${visit}`).digest("base64")}`;
});
app.listen(3000);
console.log("Server running at http://127.0.0.1:3000/");

npm i uuid

const Koa = require("koa");
const Router = require("@koa/router");
const uuid = require("uuid");
const app = new Koa();
let router = new Router();
app.use(router.routes());
app.keys = ["kaimo"];
const session = {};
const cardName = "kaimo.sid"; // 卡的名字，标识店铺名
router.get("/visit", async (ctx, next) => {
    let cardId = ctx.cookies.get(cardName);
    if (cardId && session[cardId]) {
        session[cardId].count--;
        ctx.body = `你有${session[cardId].count}次机会`;
    } else {
        let cardId = uuid.v4();
        session[cardId] = { count: 3 };
        ctx.cookies.set(cardName, cardId);
        ctx.body = `你有${session[cardId].count}次机会`;
    }
});
app.listen(3000);
console.log("Server running at http://127.0.0.1:3000/");

npm i koa-session

const Koa = require("koa");
const Router = require("@koa/router");
const session = require("koa-session");
const app = new Koa();
let router = new Router();
app.use(session({}, app));
app.use(router.routes());
app.keys = ["kaimo"];
router.get("/visit", async (ctx, next) => {
    ctx.session.visit = ctx.session.visit || 0;
    ctx.session.visit++;
    ctx.body = `你有${ctx.session.visit}次机会`;
});
app.listen(3000);
console.log("Server running at http://127.0.0.1:3000/");