How To Write A Non-blocking If Statement In Node Js?

I have an if statement in php: if ( $isTrue && db_record_exists($id)) { ... } else { ... }; The first condition is a true / false boolean check. The second condition call

Solution 1:

Check the variable first, then check the result of the async call inside the callback.

if (isTrue) db_record_exists(id, function(r) {
    if (r) {
        // does exist
    } else nope();
});
else nope();

function nope() {
    // does not exist
}

Solution 2:

You will need to use callbacks for the if and the else part. Then "nest" the and-conditions:

if ($isTrue) {
    db_record_exists(id, function(result) {
        if (result)
            doesExist();
        else
            doesntExist();
    });
else
   doesntExist();

For convenience, you could wrap all that in a helper function (and if you need it multiple times, put in a library):

(function and(cond, async, suc, err) {
    if (cond)
        async(function(r) { (r ? suc : err)(); });
    else
        err();
})($isTrue, db_record_exists.bind(null, id), function() {
    …
}, function() {
    …
});

Solution 3:

Maybe this way?

functiondb_record_exists(id, callback) {
  db.do( "SELECT 1", function(result) { callback(result ? true : false); });
}