Duplicate of Product in Shopping Cart

2019-03-05 06:14发布

站内文章 / JavaScript
29 0 0

问题:

I have a simple problem in my shopping cart function. After i clicked the add to cart button, if it has the same product ID, it outputs a new product in a new row. It should just increase the product's quantity if it has the same product ID. 

const products = [];
const carts = [];
const inputs = {
  id: document.getElementById("productID"),
  desc: document.getElementById("product_desc"),
  qty: document.getElementById("quantity"),
  price: document.getElementById("price")
};
const productsTable = document.getElementById("products-table");
const cartsTable = document.getElementById("carts-table");

function renderProductsTable() {
  // delete all entries
  Array.from(productsTable.children).slice(1).forEach(entry => productsTable.removeChild(entry));
    
    for (product of products) {
      const tr = document.createElement('tr');
      const id = document.createElement('td');
      id.textContent = product.id;
      const desc = document.createElement('td');
      desc.textContent = product.desc;
      const qty = document.createElement('td');
      qty.textContent = product.qty;
      const price = document.createElement('td');
      price.textContent = product.price;
      const action = document.createElement('td');
      const deleteButton = document.createElement('button');
      deleteButton.textContent = 'Delete';
      deleteButton.addEventListener('click', () => removeProduct(product.id))
      const addToCartButton = document.createElement('button');
      addToCartButton.textContent = 'Add to cart';
      addToCartButton.addEventListener('click', () => addCart(product.id));
      action.appendChild(deleteButton);
      action.appendChild(addToCartButton);
      tr.appendChild(id);
      tr.appendChild(desc);
      tr.appendChild(qty);
      tr.appendChild(price);
      tr.appendChild(action);
      productsTable.appendChild(tr);
    }

}

function addProduct() {
  
  const product = {
  id: inputs.id.value,
  desc: inputs.desc.value, 
  qty: Number(inputs.qty.value),
  price: Number(inputs.price.value)
  };

  let existing = products.find(item => item.id === product.id);
  if (existing) {
  existing.qty += product.qty;
  } 
  else {
   products.push(product);
  }
  renderProductsTable();
  document.getElementById('order').reset();
  }



function removeProduct(product_id) {
  const index = products.findIndex(p => p.id === product_id);
  products.splice(index, 1);
  renderProductsTable();
}

function addCart(product_id) {
      const product = products.find(p => p.id === product_id);
      const cartItem = carts.find(c => c.product === product);
      
      if(cartItem) {
        cartItem.qty ++;
      }
      else {
        carts.push(product);
      }
      renderCartTable();
          
}

function renderCartTable() {
  for (cart of carts){
    const tr = document.createElement('tr');
    const id = document.createElement('td');
    id.textContent = cart.id;
    const desc = document.createElement('td');
    desc.textContent = cart.desc;
    const qty = document.createElement('td');
    qty.textContent = cart.qty;
    const price = document.createElement('td');
    price.textContent = cart.price;
    const total = document.createElement('td');
    total.textContent = cart.qty * cart.price
    const action = document.createElement('td');
    const subtractButton = document.createElement('button');
    subtractButton.textContent = 'Subtract Quantity';
    const addButton = document.createElement('button');
    addButton.textContent = 'Add Quantity';
    const removeButton = document.createElement('button');
    removeButton.textContent = 'Remove Item';
    tr.appendChild(id);
    tr.appendChild(desc);
    tr.appendChild(qty);
    tr.appendChild(price);
    tr.appendChild(total);
    tr.appendChild(action);
    cartsTable.appendChild(tr);
  }
}
<!DOCTYPE html>
<html>
<head>
  <title>Shopping Cart ES6</title>
</head>
<body>
  <form name="order" id="order">
    <table>
      <tr>
        <td>
          <label for="productID">Product ID:</label>
        </td>
        <td>
          <input id="productID" name="product" type="text" size="28" required/>
        </td>
      </tr>
      <tr>
          <td>
              <label for="product">Product Desc:</label>
          </td>
          <td>
              <input id="product_desc" name="product" type="text" size="28" required/>
          </td>
      </tr>
      <tr>
          <td>
              <label for="quantity">Quantity:</label>
          </td>
          <td>
              <input id="quantity" name="quantity" width="196px" required/>
          </td>
      </tr>
      <tr>
          <td>
              <label for="price">Price:</label>
          </td>
          <td>
              <input id="price" name="price" size="28" required/>
          </td>
      </tr>
  </table>
  <input type="reset" class="resetbtn" value="Reset" />
  <input type="button" id="btnAddProduct" onclick="addProduct();" value="Add New Product" >
</form>
<table border="1|1" id="products-table">
  <tr>
    <th>Product ID</th>
    <th>Product Description</th>
    <th>Quantity</th>
    <th>Price</th>
    <th>Action</th>
  </tr>
</table>
<br />
<h2>Shopping Cart</h2>
<table border="1|1" id="carts-table">
  <tr>
    <th>Product ID</th>
    <th>Product Description</th>
    <th>Quantity</th>
    <th>Price</th>
    <th>Total Amount</th>
    <th>Action</th>
  </tr>
</table>
</body>
<script src="script.js">
</script>
</html>

回答1:

So currently your code is setup that you remove all the products when adding them to the product table, however you do not do the same when adding them to the cart. So just adding this would remove everything from your cart table

Array.from(cartsTable.children).slice(1).forEach(entry => cartsTable.removeChild(entry));

There are however some minor problems with your current code, nl:

  • If you add twice the same product id, you don't validate if the price or the description is the same

  • If you add products to the carts table, you only increase the quantity by 1, however, the product itself may have a higher quantity set, so you can fix it like this

    function addCart(product_id) {
  const product = products.find(p => p.id === product_id);
  const cartItem = carts.find(c => c.product === product);

  if(cartItem) {
    cartItem.qty += product.qty;
  }
  else {
    carts.push(product);
  }
  renderCartTable();
}

  • You could use <input type="number" /> for the product quantity

  • You could use <input type="number" step="0.01" /> for the price field
  • Upon removing an item from the products table, the product should no longer be available in the cart, so you should add a call to remove the product from the cart as well
  • You have 2 functions that create a table, both could be generalized to share the same functionality

I have rewritten the function you are describing a bit, using an answer I had already given on another question which will create a table based on given columns and an array containing the data

It still has the problem that it won't validate differences in the description / price when adding the same product, but it helps for all other problems I have mentioned.

It might be a bit longer code, however, that is partly due to the table helper function which can do quite some things and might be overkill for the scenario you describe. It does however work, and made it a lot easier to integrate the table creation ;)

// will reassign when items get removed
let products = [];
// will reassign when items get removed
let cart = [];

function addOrIncrease(item, targetContainer, equality = (i) => i.id) {
  let match = targetContainer.find(i => equality(item) === equality(i));
  if (match) {
    // this could actually be a problem, eg: description and price are not validated
    // you might need to make sure that a warning pops up in case the price is different
    match.qty += item.qty;
  } else {
    // didn't find so it gets added to whichever container
    targetContainer.push(item);
  }
}

// Gets the value of the elementId or a defaultValue
function getValue( elementId, defaultValue ) {
  let elem = document.getElementById( elementId );
  if (!elem || !elem.value) {
    return defaultValue;
  }
  return elem.value;
}

// resets the value for an inputfield
function resetValue( elementId ) {
  let elem = document.getElementById( elementId );
  elem && (elem.value = null);
}

// adds a product to the list
function addProduct() {
  let product = {
    id: getValue('productId', ''),
    description: getValue('productDescription', ''),
    qty: parseInt(getValue('productQty', 1)),
    price: parseFloat(getValue('productPrice', 0))
  };
  if (product.id === '') {
    alert('Please enter a product id');
    return;
  }
  addOrIncrease( product, products );
  resetValue( 'productId' );
  resetValue( 'productDescription' );
  resetValue( 'productQty' );
  resetValue( 'productPrice' );
  renderProducts();
}

// adds an item to the cart
function addToCart(itemId) {
  var product = products.find( p => p.id === itemId );
  if (!product) {
    alert('Couldn\'t find product');
    return;
  }
  addOrIncrease( product, cart );
  renderCart();
}

// removes an item from the cart
function removeFromCart(itemId) {
  cart = cart.reduce( (current, item) => {
    if (item.id !== itemId) {
      current.push(item);
    }
    return current;
  }, []);
  renderCart();
}

// removes an item from the products list
// while simultanously removing it from the shopping cart (as it is no longer in the product list)
function removeFromProducts(itemId) {
  products = products.reduce( (current, item) => {
    if (item.id !== itemId) {
      current.push(item);
    }
    return current;
  }, []);
  renderProducts();
  // remove it from the cart, as it is no longer in the products list
  removeFromCart(itemId);
}

// renders the products to the table
// will re-render the full table each time
function renderProducts() {
  createTable('products', products, [{
      title: 'id',
      field: 'id',
      class: 'left'
    },
    {
      title: 'description',
      field: 'description',
      class: 'left'
    },
    {
      title: 'quantity',
      field: 'qty',
      class: 'right'
    },
    {
      title: 'price',
      field: 'price',
      class: 'right'
    },
    {
      title: 'total',
      value: (i) => i.price * i.qty,
      class: 'right',
      template: '%0 €'
    },
    {
      title: 'action',
      field: 'id',
      class: 'center',
      template: '<button type="button" onclick="removeFromProducts(\'%0\');">Remove product</button>' +
        '<button type="button" onclick="addToCart(\'%0\');">Add to cart</button>'
    }
  ]);
}

// renders the cart to the cart table
// will rerender each time called
function renderCart() {
  createTable('cart', cart, [{
      title: 'id',
      field: 'id',
      class: 'left'
    },
    {
      title: 'description',
      field: 'description',
      class: 'left'
    },
    {
      title: 'quantity',
      field: 'qty',
      class: 'right'
    },
    {
      title: 'price',
      field: 'price',
      class: 'right'
    },
    {
      title: 'total',
      value: (i) => i.price * i.qty,
      class: 'right',
      template: '%0 €',
      calculateTotal: true
    },
    {
      title: 'action',
      field: 'id',
      class: 'center',
      template: '<button type="button" onclick="removeFromCart(\'%0\');">Remove</button>'
    }
  ]);
}

/* Helper function to create a table dynamically */
/* Taken from: https://stackoverflow.com/questions/43924509/creating-an-html-table-using-javascript-and-json/43925208#43925208 */
function createTable(target, data, columns) {
  // gets the elements required based on id for the target div
  // and creates the table, thead, tbody & tfoot for the table
  let element = document.getElementById(target),
    table = document.createElement('table'),
    thead = document.createElement('thead'),
    header = document.createElement('tr'),
    tbody = document.createElement('tbody'),
    tfoot = document.createElement('tfoot'),
    // totals is used for the totals for the footer
    totals = {};

  // creates the header
  for (const column of columns) {
    // and creates the cells in the header, adding title and class
    let cell = document.createElement('td');
    cell.innerHTML = column.title;
    cell.className = column.class;
    header.appendChild(cell);
  }
  thead.appendChild(header);

  for (const item of data) {
    // creates the single rows
    let row = document.createElement('tr');
    for (const column of columns) {
      // and for each column creates the cell itself
      let cell = document.createElement('td');
      let value;
      // checks what to display
      if (column.field) {
        // only a property on the data
        value = item[column.field];
      } else if (column.value) {
        // a function with a callback value
        value = column.value(item)
      }
      // if it should calculate totals, it will do so here
      if (column.calculateTotal) {
        // in case the column is unknown, it's initialized as 0
        // warning: all values will be whole numbers
        totals[column.field] = (totals[column.field] || 0) + parseInt( value );
      }
      // if it has a template, we will replace the %0 with value
      // this template function supports only 1 value to be "templated"
      if (column.template) {
        value = column.template.split('%0').join(value);
      }
      // set the cell value
      cell.innerHTML = value;
      // set the class (used to align, for example)
      cell.className = column.class;
      // add cell to row
      row.appendChild(cell);
    }
    // add row to tbody
    tbody.appendChild(row);
  }
  // empty object would mean false, so only if totals needed to be calculated
  // would it create the footer here
  if (totals && data.length > 0) {
    let row = document.createElement('tr');
    for (const column of columns) {
      let cell = document.createElement('td'), value = '';
      if (column.calculateTotal) {
        value = totals[column.field];
        if (column.template) {
          // can still use the row template
          value = column.template.split('%0').join(value);
        }
      }
      cell.innerHTML = value;
      cell.className = column.class;
      row.appendChild( cell );
    }
    tfoot.appendChild( row );
  }
  table.appendChild(thead);
  table.appendChild(tbody);
  table.appendChild(tfoot);
  // clear the target element
  element.innerHTML = '';
  // set the table on the target element
  element.appendChild(table);
}

// start of the application, create the 2 tables
// and then it's up to the user
renderProducts();
renderCart();
.left {
  text-align: left;
}
.right {
  text-align: right;
}
thead tr {
  background-color: #777;
}
thead tr td {
  font-weight: bold;
  color: #fff;
}
tfoot tr td {
  font-weight: bold;
}
table td {
  padding: 5px;
  border-bottom: solid #efefef 1px;
}
.fields > div > span:first-child {
  display: inline-block;
  width: 120px;
}
.fields > div {
  margin: 5px;
}
<div class="fields">
  <div>
    <span>ItemID:</span>
    <span><input type="text" id="productId" placeholder="Item Id" /></span>
  </div>
  <div>
    <span>Description:</span>
    <span><input type="text" id="productDescription" placeholder="Product description" /></span>
  </div>
  <div>
    <span>Quantity:</span>
    <span><input type="number" min="1" id="productQty" placeholder="Quantity" /></span>
  </div>
  <div>
    <span>Price:</span>
    <span><input type="number" min="0" step="0.01" id="productPrice" placeholder="Price" /></span>
  </div>
  <button type="button" onclick="addProduct()">Add to product list</button>
</div>
<h1>Products</h1>
<div id="products">
</div>
<h1>Shopping cart</h1>
<div id="cart">
</div>



回答2:

It's been almost 2 years... But the solution is simple actually:

First, try to spit out the name of your product on the console... the value has spaces ! ! !

This means that the cart is adding the raw values without any processing, therefore the condition to match the name and price will never be true, hence the duplicates.

Solution 1 (tedious): Trim spaces of all values prior to adding to the cart.

Solution 2 (preferred): Don't add any spaces between the values and the HTML tags!

"<strong class="item_price">price</strong>"

<!-- "NOT -->

"<strong class="item_price">
    price
</strong>"



标签： javascript arrays ecmascript-6 javascript-objects
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