Javascript / JQuery scope

Question

I have a couple of functions in Javascript / Jquery where I am passing a property to one function in turn passes down to another function.

The problem that I am getting is that the property in the first function has been populated but the second function the property is underfined.

ExecuteSQL: function (sql, onSuccess) {                
    try {
        if (this.Database != null) {
            this.Database.transaction(function (tx) {
                tx.executeSql(sql, [], function (d, r) {
                    if (this.onSuccess) this.onSuccess(r);
                });
            });
        }
        else {
            alert("Could not execute SQL, the database connection is closed.");
        }

    }
    catch (e) {
        alert("Failed to execute SQL," + e);
    }
},

The onSuccess is a value at the ExecuteSQL scope but empty in the transaction scope.

Any help would be great.

Thanks Paul.

PSL · Accepted Answer · 2013-12-06 01:22:25Z

2

In this case you can just do:

function (d, r) { if (onSuccess) onSuccess(r); }

Just to make the check explicitly for function you can do:

function (d, r) { if (typeof onSuccess === 'function') onSuccess(r); }

Since onSuccess is a variable that holds the function reference that is defined in the scope of the function ExecuteSQL you can just access it as is inside the callback and it is not associated as a property of the instance, so this.onSuccess doesn't fetch you anything (Leaving the fact that this is not the this inside the ExecuteSQL function ).

edited Dec 6, 2013 at 1:22

answered Dec 5, 2013 at 22:46

PSL

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1 Comment

Paul Over a year ago

Hi, thank you, I did try that before but could get it to work either but this was because of another JS problem. Thanks.

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