javascript - 未捕获的TypeError:无法调用未定义的方法“XXX”

我在第一次尝试javascript oop时遇到了一个漩涡，我得到了一个错误：
uncaught typeerror:无法调用未定义的方法“addweight”
它抱怨的是weight.webdb.addWeight下的一个方法正在从全局函数addWeight调用。

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);
}

演示：http://jsfiddle.net/SMbL3/1/

最佳答案

函数中定义的局部变量weight正在外部作用域中隐藏weight变量。只需调用函数局部变量，比如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);
}