yes, You can populate drop down list using Javscript and Web method.
use javascript to call web method which will return data that is to be bind with drop down list in the form of string array, and after that in javascript bind that data with drop down list. as follows:
function bindDdl() {
try {
var ddl = document.getElementById('ddl1');
var x = PageMethods.GetData('', onsuccess, onfail);
}
catch (e) {
alert(e);
}
}
function onsuccess(result) {
try {
var ddl = document.getElementById('ddl1');
var count= ddl.options.length;
while (ddl.options.length > 0) {
ddl.options.remove(0);
}
for (var i = 0; i < result.length-1; i=i+2) {
var opt = document.createElement("option");
opt.text = result[i];
opt.value = result[i+1];
ddl.options.add(opt);
}
}
catch (e) {
alert(e);
}
}
GetData(string str) is the page method which return string array.