运行正则表达式搜索并再次替换javascript

I have this code:

我有这个代码:

<script type="text/javascript">
document.addEventListener("DOMContentLoaded", function(event) {
var field1 = document.getElementById("field_lp_video");
field1.addEventListener("input", combineFields);
function combineFields(){
    var val1 = field1.value;
    var regExp = /^.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/;
    var val1match = val1.match(regExp);
    var val1re = val1match[2];
    var oldURL = document.getElementById("changeThisMovie").innerHTML;
    var oldURLmatch = oldURL.match(regExp);
    var res = oldURL.replace("yeC3AisTs2Y", val1re);
    document.getElementById("changeThisMovie").innerHTML = res;
}
});
</script>
<script type="tex