关于select的 options无法取值

Question

 Ext.Ajax.request({
            url: "ExtjsProduct.aspx",
            success: function (response) {
                var StrPro = document.getElementById("StrPro").value;
                var StrValue = document.getElementById("StrValue").value;                var tmp = response.responseText;
                var menusArray = Ext.util.JSON.decode(response.responseText);                for (var k = 0; k < menusArray.length; k++) {
                    if (menusArray[k]["ProPertyName"] != null) {
                        document.getElementById("Perty1").options.add(new Option(menusArray[k]["ProPertyName"]));
                    }
                    if (menusArray[k]["ProValueName"] != null) {
                        document.getElementById("PertyValue1").options.add(new Option(menusArray[k]["ProValueName"]));
                    }
                }
                alert(pm);
                //pm的值是24 没有问题。
                var pm = document.getElementById("Perty1").options.length;                for (var v = 0; v < pm.length; v++) {
                    //document.getElementById("Perty1").options[v].value的值为空。为什么
                    if (document.getElementById("Perty1").options[v].value == StrPro) {
                        document.getElementById("Perty1").options[v].selected = true;
                    }
                }function

Answer 1

你试一下，
//document.getElementById("Perty1").options[v].value的值为空。为什么options改为option

Answer 2

 var pm = document.getElementById("Perty1").options.length;                for (var v = 0; v < pm.length; v++) {
                    //document.getElementById("Perty1").options[v].value的值为空。为什么
                    if (document.getElementById("Perty1").options[v].value == StrPro) {
                        document.getElementById("Perty1").options[v].selected = true;
                    }
                }
pm为options的length，再取一次length...

Answer 3

var pm = document.getElementById("Perty1").options.length;                for (var v = 0; v < pm.length; v++) {

Answer 4

setTimeout(function(){ 
    var pm = document.getElementById("Perty1").options.length;
 
                for (var v = 0; v < pm.length; v++) {
                     //document.getElementById("Perty1").options[v].value的值为空。为什么
                     if (document.getElementById("Perty1").options[v].value == StrPro) {
                         document.getElementById("Perty1").options[v].selected = true;
                     }
                 } 
}, 10);