selectedOptions [0] .textContent;不在IE或Firefox中工作

function call(op) {
    var x = op.selectedOptions[0].textContent;
    var n = x.substring(0, 3);
    //alert(n);
    document.pts.inputbox.value = n;
    document.pts.submit();
}
function call(op) {
    var x = op.selectedOpti