如何在javascript的下拉列表中预先选择一个选项？

Question

我有一个下拉代码

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”作为默认值的代码是什么？ 在HTML中是这样的

selected="selected"

在javascript中呢？

Answer 1

你需要使用

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

请注意右侧的1。 多数民众赞成意味着选择

Answer 2

我可以建议您使代码更简洁，例如：

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) );
}

对我来说，这感觉更好，因为只要您想更改一个值，就可以在数组中更改它的值。 而且这也可以单独重构为仅接受数组和选择框以将项目加载到其中的函数。

（经过chrome测试，但应该可以在大多数地方使用；您可以在w3schools上找到针对IE6进行修复的黑客工具。此外，如果选择框中包含项，那么它们将保留。您可能要先使用来自此处的代码： http : //www.plus2net.com/javascript_tutorial/list-remove.php ）

Answer 3

尝试这个：

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