LIFF_Parameters_passing.js

const queryString = decodeURIComponent(window.location.search)
      .replace("?liff.state=", "")
      .substr(1);
console.log(queryString);
    liff.ready.then(() => {
      if (!liff.isLoggedIn()) {
        liff.login({
          redirectUri:
            "https://tutorial.sirateek.me/LIFF/page2.html?" + queryString,
        });
      } else {
        console.log("Logged in");
        window.location.href = "page2.html?" + queryString;
      }
    });

    liff.init(
      {
        liffId: "LIFF ID",
      },
      () => {},
      (err) => {
        console.log(err);
        window.alert(err);
      }
    );