How can I define a variable inside a function to be called by an event
function testSet(elmA,elmB) {
    elmA.onclick = function() {
        elmB.value = "ok";
    };
}

testSet(document.getElementById('a'),document.getElementById('b'));

var globalElmB = something;

function testSet(elmA,elmB){
    globalElmb = elmB;
    elmA.onclick=function(){

        globalElmb.value="ok";
    }
}