我一直在“无法获取未定义或空引用的属性”长度”

Question

I'm testing independent pieces of a larger piece of code for functionality in MS CRM and I want to know why I keep getting the above error for this small piece of code:

function testThis()
{
    var optionset = document.getElementById("new_makeyear");
    console.log("this is supposed to be something " + optionset.Options.length);
}

"new_makeyear" is an option set. The log statement was just so I can see the behavior through the console. What's the problem?

Thanks

Answer 1

As Henk mentioned in his comment, you shouldn't access the DOM. You should use the API to inspect the options of an option set, like this:

function testThis() {
    var makeYear = Xrm.Page.getAttribute("new_makeyear");
    if (!makeYear) { return; }
    console.log(makeYear.getOptions().length + " options currently available");
}

Answer 2

如果您设法访问生成的DOM（例如通过onchange事件），则可以使用选项组， if(this.options[this.selectedIndex].parentNode.tagName =='optgroup') var og = this.options[this.selectedIndex].parentNode.label;