Question

我有下拉列表的代码

if (chosen == "Parade") {
  selbox.options[selbox.options.length] = new Option("Select Venue","");
  selbox.options[selbox.options.length] = new Option("Benavides Park","Benavides Park");
  selbox.options[selbox.options.length] = new Option("CME Auditorium","CME Auditorium");
  selbox.options[selbox.options.length] = new Option("Engineering Sports Complex","Engineering Sports Complex");
  selbox.options[selbox.options.length] = new Option("Field in front of Grandstand","Field in front of Grandstand");
  selbox.options[selbox.options.length] = new Option("Plaza Mayor","Plaza Mayor");
  selbox.options[selbox.options.length] = new Option("Quadricentennial Park","Quadricentennial Park");
  selbox.options[selbox.options.length] = new Option("Rectors Hall","Rectors Hall");
  selbox.options[selbox.options.length] = new Option("Seminary Gym","Seminary Gym");
  selbox.options[selbox.options.length] = new Option("Tinoco Park","Tinoco Park");
  selbox.options[selbox.options.length] = new Option("UST Grandstand","UST Grandstand");
  selbox.options[selbox.options.length] = new Option("UST Gymnasium","UST Gymnasium");
  selbox.options[selbox.options.length] = new Option("Venue not listed/outside UST","Venue not listed/outside UST");
}

选项“Benavides Park”的默认值是什么代码？在HTML中，它就像这样

selected="selected"

在javascript中怎么样？

Answer 1

你需要使用

new Option("UST Grandstand","UST Grandstand", 1);

注意右边的1。这意味着选择

Answer 2

我建议您使代码更清晰，如下所示：

var selectedItem = -1; // change to select different item
var options = ["Benavides Park", "CME Auditorium", "Engineering Sports Complex", "Field in front of Grandstand", "Plaza Mayor", "Quadricentennial Park", "Rectors Hall", "Seminary Gym", "Tinoco Park", "UST Grandstand", "UST Gymnasium", "Venue not listed/outside UST"];

selbox.add( new Option("Select Venue", "", (-1 == selectedItem) ? 1 : 0));
for (var i = 0; i < options.length; i++) {
   selbox.add( new Option(options[i], options[i], (i == selectedItem) ? 1 : 0) );
}

对我而言，这感觉更好，因为无论何时想要更改值，您只需更改其在数组中的值。这也可以重构为它自己的函数，只接受一个数组和选择框来加载项目。

（在Chrome中测试但应该在大多数地方都可以使用;你可以在w3schools找到一个黑客来修复IE6。此外，如果选择框中有项目，那么它们将保留。你可能想要清除它首先使用此处的代码：http://www.plus2net.com/javascript_tutorial/list-remove.php）

Answer 3

试试这个：

var foo = document.getElementById('yourSelect');
if (foo)
{
  foo.selectedIndex = 0;
}

如何在javascript的下拉列表中预先选择一个选项？

3 个答案: