​x
 
<!DOCTYPE html>
<html>
<body>
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<h1>Math.sign()</h1>
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<p>单击该按钮可找出不同的数字是正数还是负数：</p>
​
<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.sign(3);
  var b = Math.sign(-3);
  var c = Math.sign(0);
  
  var x = a + "<br>" + b + "<br>" + c;
  document.getElementById("demo").innerHTML = x;
}
</script>
​
</body>
</html>
​