Question

I’m giving JavaScript OOP a swirl for the first try and I’m getting this error:

Uncaught TypeError: Cannot call method ‘addWeight’ of undefined

It is complaning about a method that is under weight.webdb.addWeight which is being called from a global function addWeight.

var weight = {};
weight.webdb = {};
weight.webdb.db = null;

weight.webdb.addWeight = function() {
    var db = weight.webdb.db;
    db.transaction(function(tx) {
        var addedOn = new Date();
        tx.executeSql('INSERT INTO weight(input,comment,date) VALUES (?,?,?)', [inputWeight, inputComment, addedOn], weight.webdb.onSuccess, weight.webdb.onError);
    });
};

function addWeight(){
    var weight = document.getElementById('inputWeight');
    var comment = document.getElementById('inputComment');  
    weight.webdb.addWeight(weight.value,comment.value); 
}

Demo: http://jsfiddle.net/SMbL3/1/

Answer 1

Your local variable weight defined in the function is shadowing the weight variable in the outer scope. Just call the function-local variable something else, like weight_elem:

function addWeight() {
    var weight_elem = document.getElementById('inputWeight');
    var comment_elem = document.getElementById('inputComment');  
    weight.webdb.addWeight(weight_elem.value, comment_elem.value); 
}