ouput標籤詳解

屬性

<output name="o1" for="a b"></output>

output標籤用於顯示計算結果，而被計算得數從哪來？從for屬性的指向來，注意從for屬性獲取的元素value爲string類型，計算時需要轉換爲number，parseInt或者+都可以。

HTML寫法

<form id="form" oninput="o1.value = (+a1.value) + (+b1.value); o2.value = (+a2.value) * (+b2.value)">
    <p>sum</p>
    <input type="number" value="0" name="a1" step="1"> +
    <input type="number" value="0" name="b1" step="1"> =
    <output name="o1" id="output1" for="a1 b1"></output>
    <p>minus</p>
    <input type="number" value="0" name="a2" step="1"> -
    <input type="number" value="0" name="b2" step="1"> =
    <output name="o2" id="output2" for="a2 b2"></output>
</form>

上面的name屬性都可以用id屬性替換。

JS寫法

<script type="text/javascript">
    form = document.getElementById('form');
    var input1 = form.elements['a1'];
    var input2 = form.elements['b1'];
    var ouput1 = form.elements['o1'];

    var input3 = form.elements['a2'];
    var input4 = form.elements['b2'];
    var ouput2 = form.elements['o2'];

    form.addEventListener('input',function () {
        ouput1.value = (+input1.value) + (+input2.value);
        ouput2.value = (+input3.value) - (+input4.value);
    });
</script>