如何使用JavaScript设置多项选择的值 [英] How to set values of multiple select using JavaScript
问题描述
要使用JavaScript设置<input>
元素的数据,我们按如下所示分配该元素的值和名称:
To set data of an <input>
element using JavaScript, we assign the value and name of that element like this:
var form = document.createElement("form");
var element = document.createElement("input");
element.value=value;
element.name=name;
在具有multiple
属性的<select>
情况下,如何设置该选择元素的值?例如,如何设置下面的myselect
元素的值:
In the case of a <select>
where the multiple
attribute is present, how do I set the value of that select element? For instance, how would I set the value of the myselect
element below:
<form method="post" action="/post/" name="myform">
<select multiple name="myselect" id="myselect">
<option value="1">option1</option>
<option value="2">option2</option>
...
我尝试通过执行此myselect.value=[1,2]
来设置值,但是它不起作用.选择option1
和option2
之后,我希望它返回[1,2]
,但只返回"1".
I tried to set the value by doing this myselect.value=[1,2]
however it does not work. After selecting option1
and option2
I expected that it returns [1,2]
, but it just returns "1".
推荐答案
要以编程方式在多选中设置多个值选项,需要将selected
属性手动添加到要选择的<option>
元素中.
To programmatically set multiple value options on a multi-select, you need to manually add selected
attributes to the <option>
elements that you want to select.
一种解决方法如下:
const select = document.getElementById('myselect')
const selectValues = [1, 2];
/* Iterate options of select element */
for (const option of document.querySelectorAll('#myselect option')) {
/* Parse value to integer */
const value = Number.parseInt(option.value);
/* If option value contained in values, set selected attribute */
if (selectValues.indexOf(value) !== -1) {
option.setAttribute('selected', 'selected');
}
/* Otherwise ensure no selected attribute on option */
else {
option.removeAttribute('selected');
}
}
<select multiple name="myselect" id="myselect">
<option value="1">option1</option>
<option value="2">option2</option>
<option value="3">option3</option>
<option value="4">option4</option>
</select>
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