I get a client is not defined
error out of the following code:
var mysql = require('mysql');
var conf = {
'database':'database',
'user':'user',
'password':'password'
};
function mysqlQuery(mysql, conf, query, callback) {
var client = mysql.createClient({
user:conf.user,
password:conf.password
});
client.query('USE ' + conf.database, function () {
client.query(query, callback);
});
}
mysqlQuery(
mysql,
conf,
'SELECT * FROM users;',
function selectCb(err, results) {
if (err) {
throw err;
}
console.log(results);
client.end();
}
);How can I pass the client variable to my callback function? I have no control on how the callback function will be called as it is called by the mysql module.
Problem courtesy of: Simon Jodet
Solution
You could
bind
[docs]
client
to callback
. Inside the callback it will be available as this
then:
client.query(query, callback.bind(client))
and
this.end();
You could also pass it as first parameter:
client.query(query, callback.bind(null, client))
or
client.query(query, function(err, results) {
callback(client, err, results);
}); where callback
is defined as
function selectCb(client, err, results) {..};Solution courtesy of: Felix Kling
