JavaScript 如何从一个函数中获取目标值并乘以选中复选框的元素值

Question

我的代码中有两个函数。当您单击指向 increase/decrease 值的箭头时，第一个函数“addItem”获取每个单独输入字段的值。第二个功能“checkbox”验证复选框是否已启用，如果已启用，则将预设数值添加到运行总数。我很难弄清楚的是如何获取输入字段值并将其乘以复选框值，只有在启用复选框时才将其添加到我的总数中。以同样的方式，如果我要将复选框切换到未选中状态，我将从总数中删除该值。现在，它所做的只是在启用复选框时将复选框值添加到运行总计中，但在递增或递减时不考虑输入字段值。我希望它在用户更改输入值并启用复选框时动态计算总数。我希望我的解释是有道理的。我的代码如下。当然，我会在代码中添加一些额外的东西，但除非我让这部分工作，否则我无法继续前进。感谢任何反馈，谢谢。

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta class="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" type="text/css" href="style.css">
    <title>Restaurant | Online Menu</title>
    <link rel="shortcut icon" href="images/pngtree-green-leaf-icon-graphic-design-template-vector-png-image_3990501.jpg" type="image/x-icon" />
</head>
<div class= "nav-container">
    <nav id= "nav-bar">
        <a href= "index.html" class="active-link">Menu</a>
        <a href= "about.html">About</a>
        <a href= "Checkout.html">Checkout</a>
    </nav>
</div>
<button id= "remove-button">Remove All</button>
<div id= "item-container">
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox" value= "10"> Item#1  
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "1" max="10" style="width: 100px"> <button class= "remove-button">Remove</button> <br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "8"> Item#2 
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "1" max="10" style="width: 100px"> <button class= "remove-button">Remove</button><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "6"> Item#3 
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "1" max="10" style="width: 100px"> <button class= "remove-button">Remove</button><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "4"> Item#4 
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "1" max="10" style="width: 100px"> <button class= "remove-button">Remove</button><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "2"> Item#5 
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "1" max="10" style="width: 100px"> <button class= "remove-button">Remove</button><br><br>
    </div>
    
<div id= "Total-Display">
    <h3 id="display-total">Current Total $
        <span id= "total-text"></span>
    </h3>
</div>
<button id= "btn-checkout">Checkout</button>
<script src= "functions.js"></script>
<body>
    <script src= "checkout-cart.js"></script>    
</body>
</html>

functions.js

const counterItems= document.getElementsByClassName('counter-Items')
const itemCheckBox =  document.getElementsByClassName('checkbox')
const removeBtn= document.getElementById('remove-button')
const btnCheckout= document.getElementById('btn-checkout')

let total = JSON.parse(localStorage.getItem('myValue'))
document.getElementById('total-text').innerText = total

retrieveDOMElementsState()

btnCheckout.addEventListener('click', onClickBtnCheckout)
function onClickBtnCheckout () {
    location.assign("/Checkout.html")
}

function retrieveDOMElementsState() {
    let saveChkBxState= JSON.parse(localStorage.getItem('saveChkBxState')) || []
    let inputFieldStoreValue= JSON.parse(localStorage.getItem('inputFieldStoreValue')) || []
    Array.from(itemCheckBox).forEach((itemCheckBoxItem, aIndex)=> {
        saveChkBxState.forEach((saveChkBxStateItem, bIndex) => {
            saveChkBxStateItem===true && aIndex===bIndex ? itemCheckBoxItem.setAttribute('checked', true) : false          
        })
        return retrieveDOMElementsState
})

    Array.from(counterItems).forEach((counterItemsItems, aIndex)=>{
        Array.from(inputFieldStoreValue).forEach((inputFieldStoreValueItem, bIndex)=>{
            aIndex===bIndex ? counterItemsItems.value= inputFieldStoreValueItem : false
        })
    })
}

Array.from(counterItems).forEach(item=> {
    item.addEventListener('change', onFieldChange) 
})

Array.from(itemCheckBox).forEach(item=> {
        item.addEventListener('change', onCheckBoxChange)
})

function onCheckBoxChange (e) {
    let checkbox = e.target
    let inputField = checkbox.nextElementSibling
    let price = checkbox.value
    let quantity = inputField.value
    calcTotal(price, quantity, e.target.checked)
    updateTotal() 
}

function onFieldChange(e){
    let saveChkBxState= Array.from(itemCheckBox).map(item=>{
        return item.checked
    })
    localStorage.setItem('saveChkBxState', JSON.stringify(saveChkBxState))

    let inputFieldStoreValue= Array.from(itemCheckBox).map(item=>{
        return item.nextElementSibling.value
     })
    localStorage.setItem('inputFieldStoreValue', JSON.stringify(inputFieldStoreValue))

    let inputField = e.target;
    let checkbox = inputField.previousElementSibling;
    let quantity = parseInt(inputField.value);
    if(quantity < 0 || quantity > 10){
      quantity = inputField.value = 0; 
    }
    inputField.value = quantity;
    if(checkbox.checked){
      let price = checkbox.value;
      let prevValue = inputField.prevValue;
      calcTotal(price, prevValue, false);
      calcTotal(price, quantity, true);
      updateTotal();
    }
    inputField.prevValue = quantity;
}

function calcTotal(price, quantity, add=true){
    price = price || 0;
    quantity = quantity || 0;
    if(add){
      total+=(price*quantity);
    }else{
      total-=(price*quantity);
    }
    localStorage.setItem('myValue', JSON.stringify(total))
}

function updateTotal(){
  document.getElementById('total-text').innerText = total;
}

removeBtn.addEventListener('click', onClickRemove)
function onClickRemove () {
    localStorage.clear()
    Array.from(itemCheckBox).forEach(item=>{
        item.checked= false
    })
    Array.from(counterItems).forEach(item=>{
        item.value= ''
    })
    total= 0
    updateTotal();
    
}

Answer 1

我已对代码进行了一些更改以使其按您的预期工作。

CodePen Demo Link

const counterItems= document.getElementsByClassName('counter-Items');
const itemCheckBox =  document.getElementsByClassName('checkbox');
let total = 0;

for (let i = 0; i < counterItems.length; i++) {
    counterItems[i].addEventListener('change', onFieldChange);
}
for (let i = 0; i < itemCheckBox.length; i++) {
    itemCheckBox[i].addEventListener('change', onCheckboxChange);
}

function onCheckboxChange(e){
    let checkbox = e.target;
    let inputField = checkbox.nextElementSibling;
    let price = checkbox.value;
    let quantity = inputField.value;
    calcTotal(price, quantity, e.target.checked);
    updateTotal();
}

function onFieldChange(e){
    let inputField = e.target;
    let checkbox = inputField.previousElementSibling;
    let quantity = parseInt(inputField.value);
    //This condition is included in your code.
    if(quantity < 0 || quantity > 10){
      quantity = inputField.value = 0; 
    }
    inputField.value = quantity;
    if(checkbox.checked){
      let price = checkbox.value;
      let prevValue = inputField.prevValue;
      calcTotal(price, prevValue, false);
      calcTotal(price, quantity, true);
      updateTotal();
    }
    inputField.prevValue = quantity;
}

function calcTotal(price, quantity, add=true){
    price = price || 0;
    quantity = quantity || 0;
    if(add){
      total+=(price*quantity);
    }else{
      total-=(price*quantity);
    }
}

function updateTotal(){
  document.getElementById('total-text').innerText = total;
}

<nav>
    <button id= "Menu">Menu</button>
    <button id= "Cart">Cart</button>
    <button id= "About-us">About Us</button>
</nav>
<div id= "item-container">
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox" value= "10"> Item#1  | Add To Order 
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "8"> Item#12  | Add To Order
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "6"> Item#3  | Add To Order
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "6"> Item#3  | Add To Order
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "4"> Item#4  | Add To Order
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
    <div class= "item-row">
        <input type= "checkbox" class= "checkbox"  value= "2"> Item#5  | Add To Order
        <input class= "counter-Items" type= "number" placeholder= "How many?" min= "0" max="10" style="width: 100px"><br><br>
    </div>
<div id= "Total-Display">
    <h3 id="display-total">Current Total (without taxes) $
        <span id= "total-text">0</span>
    </h3>
</div>

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