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上图是history在chrome控制台的显示，原型链中的函数有6个，其中的5个能被for in遍历，但是有一个又不行，为什么啊？而且不行的那个constructor在chrome控制台显示的颜色都比其他的淡
history
for in
constructor
只有具有 Enumerable （可枚举）属性的属性才能被 for ... in 遍历。constructor是最常见的不可枚举属性之一。
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_propertieshttps://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor
对于你的问题就参考上面的解释， 还有函数就5个。看你截图的length，已经明确告诉你了。
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
只有具有 Enumerable （可枚举）属性的属性才能被 for ... in 遍历。
constructor是最常见的不可枚举属性之一。https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor
对于你的问题就参考上面的解释， 还有函数就5个。
看你截图的length，已经明确告诉你了。