问禁用HTML列表框中的一个选项

EN

<select id="select1">
    <option value="">Choose</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
</select>

<select id="select2">
    <option value="">Choose</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
</select>

<select id="select3">
    <option value="">Choose</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
</select>

var previousValues = []
    $selects = $('#select1, #select2, #select3');

$selects
    .mousedown(function(e) {
        // save the previous value for re-enabling it when you change
        var val = $(this).val();
        if (val) {
            previousValues[this.id] = val;
        }
    })
    .change(function(e) {
        // get the other select elements
        var $theOtherSelects = $selects.not('#' + this.id),
            prevVal = previousValues[this.id],
            val = $(this).val();

        // re-enable the previously disabled option
        if (prevVal) {
            $theOtherSelects
                .find('option[value=' + prevVal + ']')
                .prop('disabled', false);
        }

        // if a value is selected, disble in the other selects            
        if (val) {
            $theOtherSelects
                .find('option[value=' + val + ']')
                .prop('disabled', true);
        }
    })
    .mousedown()
    .change();