如何使用javascript在输入选择（HTML）中设置a字段？

我将随机选择一个数字，并用排序后的数字在select中定义所选字段。如何设置字段？

将属性selected=“selected”添加到要选择的选项元素中

伪代码

function foo()
{
create list of option elements
generate random number
get a single option element at index of random number
set all options attribute "selected" = null
set the option element[at index of random number] attribute selected = "selected"
}

---

将属性selected=“selected”添加到要选择的选项元素中

伪代码

function foo()
{
create list of option elements
generate random number
get a single option element at index of random number
set all options attribute "selected" = null
set the option element[at index of random number] attribute selected = "selected"
}