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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript Date 对象</h1>
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<p>这个“自制的” isDate () 函数在日期上使用时返回 true：</p>
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<p id="demo"></p>
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<script>
const myDate = new Date();
document.getElementById("demo").innerHTML = isDate(myDate);
​
function isDate(myDate) {
  return myDate.constructor.toString().indexOf("Date") > -1;
}
</script>
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</body>
</html>
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