Buttons无法正常工作

Question

请容忍我，因为我刚刚接触Javascript，而且我在JavaScript的面向对象编程方面完全是新手，所以……有人能帮我解决我的问题吗？(请原谅代码中的长度和注释)

首先:我已经创建了两个对象:产品，篮子通过'createProductRows()‘函数传入一个产品对象数组在加载时创建了一个表。这将打印出产品信息并创建一个按钮，该按钮将产品添加到篮子中。这是按钮(或其他东西)给我的问题。*我希望按钮使用productList数组中的产品索引调用addProduct()函数，而该数组又调用篮子对象中的两个函数: addToBasket()和display()。这应该会将创建的元素添加到购物篮表中

我不确定我是否正确地传递了productList数组，或者也许我应该使用篮子方法的原型，任何帮助让它正确工作的人都将不胜感激。谢谢

var productList = []; // array where product objects are to be held
var basket;
var obj;

//product constructor
var Product = function(name, description, quantity, price, gender) { 
    obj = this; // a reference to this object //could use
    this.name = name;
    this.description = description;
    this.quantity = quantity;
    this.price = price.toFixed(2);
    this.gender = gender;
};
    //product prototypes
    Product.prototype = {
        toString: function() { return this.name.toLowerCase(); }
    };
    Product.prototype.getPrice = function() {
        return '\u00A3' + this.price;
    };
    Product.prototype.getQuantity = function() {
        return this.quantity;
    };

//instantiate new products 
var shorts = new Product('Shorts', 'Stone Wash Demin Shorts', 20, 25.90, 'F');
var bag = new Product('Bag', 'Leather Shoulder Bag', 4, 50.45, 'F');
var blouse = new Product('Blouse', 'Vintage Blue Silk Polka Dot Blouse', 8, 45.99, 'F');
var boots = new Product('Boots', 'Soft Leather Brown Ankle Boots', 3, 65.35, 'F');
var belts = new Product('Belts', 'Woven Finish Fashion Belt', 15, 21.99, 'F');
var shirt = new Product('Shirt', 'Jacquard Pattern Wrangler Western Shirt', 19, 34.87, 'M');
var shoes = new Product('Shoes', 'Suede Ankle Boots', 6, 55.00, 'M');
var trousers = new Product('Trousers', 'Izod Peach Chinos', 23, 31.75, 'M');
var belt = new Product('Belt', 'Suede Casual Belt', 4, 22.98, 'M');
var hat = new Product('Hat', 'Trilby Style Brown Woven Fix', 2, 67.80, 'M');

//push all product objects to an array
productList.push(shorts, bag, blouse, boots, belts, shirt, shoes, trousers, belt, hat);

// basket constructor
var Basket = function(container, products) { // passes in the product list
    this.container = container; // this tells me where to add the data
    this.products = products; //reference to product values
    this.quantity = []; // stores quantities in bag

    for (var i=0; i < products.length; i++) { //find product

        this.quantity[i] = 0; //amount of each product in basket

        // method to add to basket
        this.addToBasket = function(index) { //reference to the product to add
            this.quantity[index]++;
            this.products[i].quantity--; // minus one from the products list
        };

        // method to remove from basket
        this.removeFromBasket = function(index) {
            if (this.quantity[index] > 0)
                this.quantity[index]--;
                this.products[i].quantity++;
        };

        //displays product
        this.display = function () {
            for (var i=0; i < this.quantity.length; i++) {
                if (this.quantity[i] > 0) {
                    var tbl = this.container
                    var row = tbl.insertRow(tbl.rows.length); // create a row element to append cells to

                    var total_price = this.quantity[i] * this.products[i].price;
                    //cell values
                    var desc = this.products[i].description; //for each value add new cell
                    var qty = this.quantity[i]
                    var price = this.products[i].price;
                    var total = total_price;
                    var remove = createRemoveBtn();

                    var cell = tbl.rows[i].insertCell(-1); // add a new cell, inserted at end of each row
                    //append cells
                    cell.appendChild(desc);
                    cell.appendChild(qty);
                    cell.appendChild(price);
                    cell.appendChild(total);
                    cell.appendChild(remove);
                    tbl.appendChild(row); // finally append the rows to the table

                    function createRemoveBtn() {
                        var btn = document.createElement('input');
                        var buttonName = products[i].name.toUpperCase(); 
                        btn.type = 'button';
                        btn.value = 'Remove';
                        btn.id = buttonName[i]; //append button names from object name
                        btn.onclick = function() {removeProduct(i);}; //test
                    return btn; 
                    };//end function 'createRemoveBtn()'
                };//end if 'quantity'
            };//end for 'basket'
        };//end function 'this.display()'
    };//end for 'products'
};//end Object 'Basket'

//create a new instance of the Basket object
basket = new Basket(document.getElementById('basketTable').getElementsByTagName('tbody')[0], productList); // *** need to create a new container for the basket

//button functions
function addProduct(item) { //add to basket function
    basket.addToBasket(item);
    basket.display();
    alert(productList[item].name + ' added to basket');
}
function removeProduct(item) { //remove item from basket
    basket.removeFromBasket(item);
    basket.display();
    alert(productList[item].name + ' removed to basket');
}

//displays product table which is called on the body onload event
function createProductRows(products) {   // passing in productList[]

    var tbl = document.getElementById('productTable').getElementsByTagName('tbody')[0]; // reference to the table to add rows to in the table body
    for (var i=0; i < products.length; i++) { // index the productsList (iterate through 0-9)

        var myProduct = products[i]; // keep a reference to each individual product - shorts, bag, blouse, etc...
        var myRow = tbl.insertRow(tbl.rows.length); // create a row element to append cells to
        var myProperties = ['name', 'description', 'quantity', 'price', 'gender']; //store the property names of the products, references to the object data

        for (var j=0; j < myProperties.length; j++) // for each property in myProperties [0-4]
        {   
            var myCell = myRow.insertCell(j); //create table cell element
            var data = myProduct[myProperties[j]]; // store property values of products
            var node = document.createTextNode(data); //add the data to a text node 
            myCell.appendChild(node); // append text node to table cell
            myRow.appendChild(myCell); // add to end of the row
        }

        var newCell = tbl.rows[i].insertCell(-1); // create a new cell, inserted at end of each row
        newCell.appendChild(createAddBtn()); // add buttons to cells
        tbl.appendChild(myRow); // finally append the rows to the table

        function createAddBtn() {
            var btn = document.createElement('input'); 
            var buttonName = products[i].name.toLowerCase(); // to be added to the button's id value
            btn.type = 'button';
            btn.value = 'Add';
            btn.id = buttonName; //append button names from object name
            btn.onclick = function() {addProduct(i);};
            return btn;
        };
    };
};

Answer 1

更新

在您的案例中，问题可能出在您创建闭包的方式上：

btn.onclick = function() {addProduct(i);};

您可以尝试登录并查看控制台，查看i的值是什么：

btn.onclick = function() {console.log('and i is:',i);addProduct(i);};

当在循环中创建闭包时，i的值并不是您所认为的值，您可能可以通过使用IIFE来解决它：

btn.onclick = (function(index) {
  return function(){
    console.log('and index is:',index);
    addProduct(index);
  };
}(i));

设置事件处理程序的问题是你得到了错误的调用对象。

下面是关于调用对象的以下answer的副本：

this变量

在所有示例代码中，您都会看到这指的是当前实例。

this变量实际上指的是调用对象，它指的是函数之前的对象。

为了解释清楚，请参阅以下代码：

theInvokingObject.thefunction();

在附加事件侦听器、回调或超时和间隔时，通常会引用错误的对象。在接下来的两行代码中，我们传递函数，但不调用它。传递函数是: someObject.aFunction，调用函数是: someObject.aFunction()。this值不是指在其上声明该函数的对象，而是指调用该函数的对象。

setTimeout(someObject.aFuncton,100);//this in aFunction is window
somebutton.onclick = someObject.aFunction;//this in aFunction is somebutton

要做到这一点，在上面的情况下引用someObject，你可以直接传递一个闭包而不是函数：

setTimeout(function(){someObject.aFuncton();},100);
somebutton.onclick = function(){someObject.aFunction();};