我正在尝试使用几个选择字段来修改数字起点。选择字段包含一些负数,因此我想相应地添加/减去。我目前无法用JQuery做到这一点 - 所以我试图弄清楚如何直接使用javascript。我已经走到了这一步,但它仅适用于单个选择领域。出于同样的原因,我不确定负数是否会减去:
<select class="select1 selectables" id="dropdown-1" name="dropdown1">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="10">Choice 1 (plus 10)</option>
<option value="-5">Choice 2 (minus 5)</option>
<option value="60">Choice 3 (plus 60)</option>
</select>
<br />
<select class="select2 selectables" id="dropdown-2" name="dropdown2">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="5">Choice A (plus 10)</option>
<option value="15">Choice B (minus 10)</option>
<option value="15">Choice C (plus 15)</option>
</select>
<br />
<select class="select3 selectables" id="dropdown-3" name="dropdown3">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="5">Choice ii (- 35)</option>
<option value="15">Choice ii (plus 15)</option>
<option value="12">Choice iii (plus 12)</option>
</select>
<script>
document.addEventListener("DOMContentLoaded", function(event) {
var gg1 = new JustGage({
id: "gg1",
value: 0
// removed elements, as this area isn't an issue
});
document.getElementById('dropdown-1').addEventListener('change', (event) => {
sum = 0;
testvar = event.target.value;
if (testvar > 0) {
sum = (sum + testvar);
alert(`up ${testvar}`);
} else if (testvar < 1) {
sum = (sum - parseInt(testvar, 10));
alert(`down ${testvar}`);
}
gg1.refresh(sum);
return false;
});
</script>
您不需要对负数进行特殊处理。只需像正数一样添加它们。在下面的代码段中,我将否定选项的值更改为实际的负值。然后calculateSum()
计算所有方框的总和。不只是改变了。虽然增量版本绝对是可能的,但没有理由只用三个盒子来实现。而这种增量变体更容易出错。
document.addEventListener("DOMContentLoaded", function(event) {
document.getElementById('dropdown-1').addEventListener('change', calculateSum);
document.getElementById('dropdown-2').addEventListener('change', calculateSum);
document.getElementById('dropdown-3').addEventListener('change', calculateSum);
});
function calculateSum() {
sum = 0;
//iterate all three boxes
for (var i = 1; i <= 3; ++i) {
var box = document.getElementById('dropdown-' + i);
var value = parseInt(box.value);
if (!isNaN(value))
sum += value;
}
alert(sum);
return false;
}
<select class="select1 selectables" id="dropdown-1" name="dropdown1">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="10">Choice 1 (plus 10)</option>
<option value="-5">Choice 2 (minus 5)</option>
<option value="60">Choice 3 (plus 60)</option>
</select>
<br />
<select class="select2 selectables" id="dropdown-2" name="dropdown2">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="10">Choice A (plus 10)</option>
<option value="-10">Choice B (minus 10)</option>
<option value="15">Choice C (plus 15)</option>
</select>
<br />
<select class="select3 selectables" id="dropdown-3" name="dropdown3">
<option disabled="disabled" selected="selected" value="">select</option>
<option value="-35">Choice ii (- 35)</option>
<option value="15">Choice ii (plus 15)</option>
<option value="12">Choice iii (plus 12)</option>
</select>