​x
 
<!DOCTYPE html>
<html>
<body>
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<p>单击该按钮可显示不同数字的以 2 为底的对数。</p>
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<button onclick="myFunction()">试一试</button>
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<p id="demo"></p>
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<script>
function myFunction() {
  var a = Math.log2(2.7183);
  var b = Math.log2(2);
  var c = Math.log2(1);
  var d = Math.log2(0);
  var e = Math.log2(-1);
​
  var x = a + "<br>" + b + "<br>" + c + "<br>" + d + "<br>" + e;
  document.getElementById("demo").innerHTML = x;
}
</script>
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</body>
</html>
​