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<!DOCTYPE html>
<html>
<body>
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<h1>JavaScript 数组</h1>
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<p>keys() 方法返回带有数组键的 Array Iterator 对象。</p>
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<p id="demo"></p>
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<script>
const fruits = ["Banana", "Orange", "Apple", "Mango"];
const keys = fruits.keys();
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let text = "";
for (let x of keys) {
  text += x + "<br>";
}
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document.getElementById("demo").innerHTML = text;
</script>
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<p>Internet Explorer 不支持 keys() 方法。</p>
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</body>
</html>
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