Hi, I'm having some problem with innerHTML. I was able to enter content into innerHTML with javascript. But how do I clear the innerHTML content and enter another new content? Below is the example problem

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<div id="testing"></div>

<script type="text/javascript">
function show1() {
document.getElementById('testing').innerHTML = "Hello World";
}
function show2() {
document.getElementById('testing').innerHTML = "Goodbye World";
}
</script>

<input type="button" value="show1" onmousedown="javascript:show1();" />
<input type="button" value="show1" onmousedown="javascript:show2();" />

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When I try it, it ended up showing "Hello WorldGoodby World" if I press "show1" then press "show2". How can I clear the content before enter new content in innerHTML?