Question

I am calling a function db.transaction with following code:

    db.transaction(createSheetDB, function(){alert("Sheet creation error!")}, function(){alert("Sheet created!")});

The function createSheetDB is a callback function which is implicitly called by db.transaction() which also passes it a parameter tx. I have implemented function createSheetDB(tx) like this:

function createSheetDB(tx) {
var nextId = getNextId();
tx.executeSql("INSERT INTO SHEET(id, name, desc) VALUES("+nextId+",'"+sheetName+"','"+desc+"')", [], 
        function(){alert("Sheet row inserted!")}, 
        function(tx, err){alert("Sheet row insertion Error: "+err.message+" "+err.code)}
);}

Now the problem is the values of sheetName and desc are available only in the calling function. How do I pass them onto function createSheetDB(tx)?

Answer 1

You can use a technique whereby you create a new callback that will close over the variables you want.

function doStuff(callback) {
    var val = 43;
    callback(val);
}

function myCallback(val, anotherVal) {
    alert("val: " + val + "\nanotherVal: " + anotherVal);
}

(function() {

    var anotherVal = "Whoa!",
        anotherCallback = function(val) {
            return myCallback(val, anotherVal);
        };

    doStuff(anotherCallback);

}());​