css計數器

css 計數器是css3，只在現代瀏覽器中有效果
counter-reset：設定某個選擇器出現次數的計數器的值。預設為 0。 就是定義一個計數器，可以定義初始值，預設是0

counter-increment：設定某個選取器每次出現的計數器增量。預設增量是 1。

demo

css 實作計數與

css

 body{
            margin: 0;
            counter-reset: increment;
        }
        input{
            border: none;
            margin: 0;
            padding: 0;
        }
        .number1 input[type=checkbox]:checked{
            counter-increment:increment 20;
        }
        .number2 input[type=checkbox]:checked{
            counter-increment:increment 30;
        }
        .number3 input[type=checkbox]:checked{
            counter-increment:increment 40;
        }
        .number4 input[type=checkbox]:checked{
             counter-increment:increment 50;
         }
        .number5 input[type=checkbox]:checked{
            counter-increment:increment 60;
        }
        .sum:after{
            content: counter(increment);

        }

html

<label class="number1"><input type="checkbox">20</label>+<label class="number2"><input type="checkbox">30</label>+<label class="number3"><input type="checkbox">40</label>+<label class="number4"><input type="checkbox">50</label>+<label class="number5"><input type="checkbox">60</label>=<p class="sum"></p>

PH