如何检查HTML选择选项中是否包含任何值

Question

In Order to stop multiple requests to server incase if the HTML Selection option is not empty

Could anybody please let me know how to check if the HTML Select is not empty

This is my HTML

<select name="" id="SCname">
     <option selected="true" style="display:none;">Select Screen</option>
</select>

var json = {
        "employees": [
            {
                "firstName": "John",
                "lastName": "Doe"
            },
            {
                "firstName": "Anna",
                "lastName": "Smith"
            },
            {
                "firstName": "Peter",
                "lastName": "Jones"
            }
        ]
};
var html = '';
for (var i = 0; i < json.employees.length; i++) {
    var firstName = json.employees[i].firstName;    
    var lastName = json.employees[i].lastName;
    html += '<option value="'+firstName+'">'+lastName+'</option>';
}
$('#SCname').append(html);
$('#SCname').show();

Could anybody please tell me how to check if this is empty or not ??

This is my jsfiddle .

Answer 1

To determine the number of options in the SELECT , using javascript:

if (document.getElementById('SCname').options.length == 1 ){  // 1 because it looks like you automatically added 1 via HTML
}

or jQuery:

if ($('#SCname option').length == 1) {...}

It's not entirely clear if you asking how to determine the current selected option or the number of options...

Answer 2

Since you are using jQuery, use the .val() method :

if ($("#SCname").val() !== "") { 
  // ... The selection is not empty.
}

Note: this requires that you're "empty" option has an empty value: value="" .

Example

---

If you also want to check if option elements exist in the select menu:

var mySelect = $("#SCname");
if (mySelect.val()!=="" && mySelect.find("option").length>0) { 
  // ... The selection is _not_ empty.
}

Answer 3

You can use the JQuery size() method on the select element option which will return the number of elements (This number should be greater than 1 since you are holding a default element):

if ($('#SCname option').size() > 1)
{
  // Do some stuff
}

---

Maybe I misuderstood your logic but, I would tell that since you are dynamically appending option elements, why not just check the lenght of employees object before doing any additional processing:

var html = '';
if (json.employees.length > 0) // Check your array size
{
  for (var i = 0; i < json.employees.length; i++) 
  { 
    var firstName = json.employees[i].firstName;
    var lastName = json.employees[i].lastName; html += ''+lastName+''; 
  } 
  $('#SCname').append(html); 
  $('#SCname').show();
}