js 实现购物车结算代码

代码描述：通过原生 js 为大家实现全选全不选购物车结算代码

HTML 代码：

<div id="container">
    <ul>
        <li>
            <input type="checkbox" name="liCheck" id="" value="">
            <button type="button" class="decrease" disabled="disabled">-</button>
            <p>
                <span class="piece">0</span>件
            </p>
            <button type="button" class="increase">+</button>
            <p>
                <span class="price">10</span>元
            </p>
            <p>
                小计:
                <input class="smallPrice" type="text" name="" id="" value="0" disabled="disabled">
            </p>
        </li>
        <li>
            <input type="checkbox" name="liCheck" id="" value="">
            <button type="button" class="decrease" disabled="disabled">-</button>
            <p>
                <span class="piece">0</span>件
            </p>
            <button type="button" class="increase">+</button>
            <p>
                <span class="price">20</span>元
            </p>
            <p>
                小计:
                <input class="smallPrice" type="text" name="" id="" value="0" disabled="disabled">
            </p>
        </li>
        <li>
            <input type="checkbox" name="liCheck" id="" value="">
            <button type="button" class="decrease" disabled="disabled">-</button>
            <p>
                <span class="piece">0</span>件
            </p>
            <button type="button" class="increase">+</button>
            <p>
                <span class="price">30</span>元
            </p>
            <p>
                小计:
                <input class="smallPrice" type="text" name="" id="" value="0" disabled="disabled">
            </p>
        </li>
        <li>
            <input type="checkbox" name="liCheck" id="" value="">
            <button type="button" class="decrease" disabled="disabled">-</button>
            <p>
                <span class="piece">0</span>件
            </p>
            <button type="button" class="increase">+</button>
            <p>
                <span class="price">40</span>元
            </p>
            <p>
                小计:
                <input class="smallPrice" type="text" name="" id="" value="0" disabled="disabled">
            </p>
        </li>
        <li>
            <input type="checkbox" name="liCheck" id="" value="">
            <button type="button" class="decrease" disabled="disabled">-</button>
            <p>
                <span class="piece">0</span>件
            </p>
            <button type="button" class="increase">+</button>
            <p>
                <span class="price">50</span>元
            </p>
            <p>
                小计:
                <input class="smallPrice" type="text" name="" id="" value="0" disabled="disabled">
            </p>
        </li>
    </ul>
    <div class="sum">
        <label>
		<input type="checkbox" name="" id="checkAll" value="">全选
	</label>
        <p>
            商品总计:
            <span id="totalCount">0</span>
        </p>
        <p>
            商品总价:
            <span id="totalPrice">0</span>
        </p>
    </div>
</div>

CSS 代码：

html,body,ul,p {
	margin:0;
	padding:0;
}
ul,li {
	list-style:none;
}
ul {
	width:450px;
}
li {
	display:flex;
	justify-content:space-around;
}
.sum {
	width:450px;
	display:flex;
	justify-content:space-around;
}
#container {
	width:450px;
	margin:100px auto;
}

JS 代码：

// 1.页面加载后执行
window.onload = function() {

    // 2.获取元素
    var liCheck = document.getElementsByName("liCheck"); //li 里面的复选框
    var decrease = document.getElementsByClassName("decrease"); //减号
    var piece = document.getElementsByClassName("piece"); //件数
    var increase = document.getElementsByClassName("increase"); //加号
    var price = document.getElementsByClassName("price"); //单价
    var smallPrice = document.getElementsByClassName("smallPrice"); //小计
    var checkAll = document.getElementById("checkAll"); //全选复选框
    var totalCount = document.getElementById("totalCount"); //总计
    var totalPrice = document.getElementById("totalPrice"); //总价

    // 3.加减按钮
    for (var i = 0; i < decrease.length; i++) {
        // 4.另存下标
        decrease[i].index = i;
        increase[i].index = i;
        liCheck[i].index = i;
        // 5.减号的点击事件
        decrease[i].onclick = function() {
            // 5-1.判断件数是否大于 0
            if (piece[this.index].innerHTML <= 1) {
                this.disabled = true; //当件数小于等于 0 时, 将减号按钮禁用
            }
            // 5-1-1.当前件数-1
            piece[this.index].innerHTML--;
            // 5-1-2.计算小计
            smallPrice[this.index].value = Number(smallPrice[this.index].value) - Number(price[this.index].innerHTML);
            // 6-4.如果当前条目是被选中状态, 则需要将该商品计入总计和总价
            if (liCheck[this.index].checked) { //选中
                totalCount.innerHTML--;
                totalPrice.innerHTML = Number(totalPrice.innerHTML) - Number(price[this.index].innerHTML);
            }
        }
        // 6.加号的点击事件
        increase[i].onclick = function() {
            // 6-1.将对应的减号解禁
            decrease[this.index].disabled = false;
            // 6-2.当前件数+1
            piece[this.index].innerHTML++;
            // 6-3.计算小计
            smallPrice[this.index].value = Number(smallPrice[this.index].value) + Number(price[this.index].innerHTML);
            // 6-4.如果当前条目是被选中状态, 则需要将该商品计入总计和总价
            if (liCheck[this.index].checked) { //选中
                totalCount.innerHTML++;
                totalPrice.innerHTML = Number(totalPrice.innerHTML) + Number(price[this.index].innerHTML);
            }
        }
        // 7.复选框的状态改变事件
        var count = 0; //存储选中个数
        liCheck[i].onchange = function() {
            // 7-1.判断是否选中	
            if (this.checked) { //选中状态
                count++;
                totalCount.innerHTML = Number(totalCount.innerHTML) + Number(piece[this.index].innerHTML); //总计加当前件数
                totalPrice.innerHTML = Number(totalPrice.innerHTML) + Number(smallPrice[this.index].value); //总计加当前件数
                // 7-1-1. 判断选中个数是否与复选框个数一致
            } else { //取消选中状态
                count--;
                totalCount.innerHTML = Number(totalCount.innerHTML) - Number(piece[this.index].innerHTML); //总计加当前件数
                totalPrice.innerHTML = Number(totalPrice.innerHTML) - Number(smallPrice[this.index].value); //总计加当前件数
            }
            count == liCheck.length ? checkAll.checked = true : checkAll.checked = false;
        }
    }

    // 8.全选复选框
    checkAll.onchange = function() {
        totalCount.innerHTML = 0; //总计置为 0
        totalPrice.innerHTML = 0; //总价置为 0
        for (var j = 0; j < liCheck.length; j++) {
            // 8-1. 将 li 里面的复选框与全选状态保持一致
            liCheck[j].checked = this.checked;
            // 8-2. 判断是否全选
            if (this.checked) {
                count = liCheck.length;
                totalCount.innerHTML = Number(totalCount.innerHTML) + Number(piece[j].innerHTML);
                totalPrice.innerHTML = Number(totalPrice.innerHTML) + Number(smallPrice[j].value);
            } else {
                count = 0;
            }
        }
    }
}

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