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<!DOCTYPE html>
<html>
<body>
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<h2>JavaScript For In</h2>
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<p>for in 语句可以遍历数组值：</p>
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<p id="demo"></p>
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<script>
const numbers = [45, 4, 9, 16, 25];
​
let txt = "";
for (let x in numbers) {
  txt += numbers[x] + "<br>"; 
}
​
document.getElementById("demo").innerHTML = txt;
</script>
​
</body>
</html>
​