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<!DOCTYPE html>
<title>Question</title>
<script>
function report(handler, _this) {
alert(
"handler:\n" + handler + "\n" +
"this: " + _this + "\n" +
"event: " + event + "\n"
)
}
</script>
<input type=button id=A value=A onclick="report(A.onclick, this)">
<script>function f() {report(B.onclick, this)}</script>
<input type=button id=B value=B onclick="f()">
<input type=button id=C value=C>
<script>C.onclick = function () {report(C.onclick, this)}</script>