​x
 
<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 数字</h1>
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<p>假如您在数学运算中使用了 NaN，则结果可能是级联：</p>
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<p id="demo"></p>
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<script>
var x = NaN;
var y = "5";
document.getElementById("demo").innerHTML = x + y;
</script>
​
</body>
</html>
​
​