Operations related to select in JavaScript _ special form Effects

JavaScript reference code for select-related operations. I. Insert option
1. DOM method
Var oSelectYear = document. getElementById ("SelectYear ");
Var op = document. createElement ("option ");
Op. innerHTML = "2010 ";
Op. value = "2010 ";
OSelectYear. appendChild (op );

2. new Option Method
Var oSelectMonth = document. getElementById ("SelectMonth ");
OSelectMonth. options. add (new Option (1, 1 ));
OSelectMonth. options. add (new Option (2, 2 ));

Ii. Clear option
Var oSelectMonth = document. getElementById ("SelectMonth ");
OSelectMonth. options. length = 0; // clear options in Select

3. Set the default option
Var oSelectMonth = document. getElementById ("SelectMonth ");
// OSelectMonth. selectedIndex = 1; // Method 1: The second item is selected by default.
// SetTimeout (function () {oSelectMonth. selectedIndex = 1 ;}, 0); // the setTimeout delay is used to prevent dom rendering problems.
// OSelectMonth. options [1]. selected = true; // method 2
OSelectMonth. options [1]. setAttribute ("selected", "true"); // method 3: setAttribute is recommended for comparison.