How to make a WebSQL query synchronous?

Question

Consider:

var globalvar;

function viewyearmain() {
  db.transaction(function (tx) 
  {
    tx.executeSql('SELECT * FROM BUDGET WHERE holdingtype="month"', [], function (tx, results) 
    {
       var len = results.rows.length;
       msg = len;
       globalvar = msg;
    }, null);

  });

  if (globalvar>0)
  {
    alert("ROWS FOUND");
  }
  else
  {
    alert("ROWS NOT FOUND");
  }
}

The problem is that ROWS NOT FOUND appears because the transaction has not completed by the time the if statement is reached.

Answer 1

Nowadays, you can take advantage of async / await and promises like this:

async function alertResult() {
  const rows = await viewyearmain();
  if (rows.length) {
    alert("ROWS FOUND");
  } else {
    alert("ROWS NOT FOUND");
  }
}

function viewyearmain() {
  return new Promise(resolve => {
    db.transaction(function(tx) {
      tx.executeSql(
        "SELECT * FROM BUDGET WHERE holdingtype = ?;", ["month"],
        function(tx, result) { resolve(result.rows); },
        null
      );
    });
  });
}