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I'm trying to figure out the correct way of passing custom data to a query call to be made available in the callback. I'm using MySQL library in nodejs (all latest versions).
I have a call to connection.query(sql, function(err, result) {...});
I couldn't find a way to 1) pass custom data/parameter to the call so that 2) it can be made available when the callback is invoked. So what is the proper way of doing so?
I have the following (pseudo-code):
... for (ix in SomeJSONArray) { sql = "SELECT (1) FROM someTable WHERE someColumn = " + SomeJSONArray[ix].id; connection.query(sql, function (err, result) { ... var y = SomeJSONArray[ix].id; }; } From the code above, I need to be able to pass the current value of "ix" used in the query to the callback itself.
How do I do that?
486
var myCallback = function(data) { console. log('got data: '+data); }; var usingItNow = function(callback) { callback('get it? '); }; Now open node or browser console and paste the above definitions.
Traditionally, the first parameter of the callback is the error value. If the function hits an error, then they typically call the callback with the first parameter being an Error object. If it cleanly exits, then they will call the callback with the first parameter being null and the rest being the return value(s).
Quick Start: How to Use MySQL in NodeCreate a new project: mkdir mysql-test && cd mysql-test . Create a package. json file: npm init -y . Install the mysql module: npm install mysql .
If you are using node-mysql, do it like the docs say:
connection.query( 'SELECT * FROM table WHERE id=? LIMIT ?, 5',[ user_id, start ], function (err, results) { } ); The docs also have code for proper escaping of strings, but using the array in the query call automatically does the escaping for you.
https://github.com/felixge/node-mysql
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