<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
</body>
<script type="text/javascript">
strTest = "1";
for ( var i = 0; i < 10; i ++ ){
strTest += strTest;
}
console.log(strTest); // 111111111111111111111111111111111...11111111111111111111111
delete strTest;
// CollectGarbage();
console.log(strTest) // undefined
</script>
</html>