Adding value from one list to another depanding on button clicked

Question

I have two multi lists. In first multi list, i got all the attributes of table by using query then now by selecting one attribute from this list, when i click on "ADD" button i want that copy of this attribute should go into another list. What i have done is i added javascript onclick function for ADD button in that i got the selected value from first multilist. But now I am not getting how to put that value in to second multi list?

What i have done in java script function is:

var index=document.getElementById("List1").selectedIndex;

var fieldval=document.getElementById("List1").options[index].value;

document.getElementById("List2").options[0].value=fieldvalue;

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But this is not working. Temporarily I am adding value at first position. Thanks in advance.

Answer 1

From here :

If you want to move an element from the first list to the second:

var index=document.getElementById("List1").selectedIndex;
var elOpt = document.getElementById('List1').options[index];
var elSel = document.getElementById('List2');

try {
  elSel.add(elOpt, null); // standards compliant; doesn't work in IE
}
catch(ex) {
  elSel.add(elOpt); // IE only
}

If you want to add one:

var index=document.getElementById("List1").selectedIndex;
var elOpt = document.getElementById('List1').options[index];
var elSel = document.getElementById('List2');

var elOptNew = document.createElement('option');
elOptNew.text = elOpt.text;
elOptNew.value = elOpt.value;

try {
  elSel.add(elOptNew, null); // standards compliant; doesn't work in IE
}
catch(ex) {
  elSel.add(elOptNew); // IE only
}