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??? ?? Student{}類，這個(gè)你可以在superSay.call(this)上面加一行console.log(this)? ?????.

?? ? ??? ???????

??? ??? ??? ?? ???? new People()? ??? ????? Instance X?? ????. new People()創(chuàng)建的實(shí)例稱為實(shí)例X。
由于superSay = Student.prototype.say，因?yàn)樯厦娴?code>Student.prototype = new People();，所以其中Student.prototype為實(shí)例X。
所以實(shí)際上superSay調(diào)用的是實(shí)例X的say，而并非People.prototype.saysuperSay = Student.prototype.say?? ?? Student.prototype = new People();??? Student.prototype? InstanceX.

People.prototype.say，主要還是原型鏈的問(wèn)題。實(shí)例X是People類的一個(gè)實(shí)例，所以實(shí)例X的所有方法會(huì)從People類的原型鏈“繼承”（用繼承這個(gè)詞，但是實(shí)際上JS的原型鏈和繼承還是有些區(qū)別的）。所以實(shí)例X.say如果沒(méi)有針對(duì)實(shí)例X重寫say方法，那么實(shí)例X的say就和People.prototype.say???? ?? ????? ???? ???

superSay.call(this)這個(gè)里面的call，只是改變了this的上下文而已。但是由于superSay即實(shí)例X.say，這個(gè)方法里根本沒(méi)有this，所以this??

? ??? js?? ?? ?????

?? ??: ?? say ???? ?? ?? ??? ?? ???? ?????. s——student.prototype——people.prototype——Object? ??? ??? ? ??? ??? ?????. ??? ???? Student.prototype? ?? ? ????. ???? ?? ??? ??? ?? ???? ? ???? ?? ? ????.

?? ??? ???? ????. ?? s.say() - 321? ????, s.jiao() - 456? ?????. ?? ?? Student.prototype.say ???? ????? ??? ??? ???? ? ??? ?????

? ?? ?? superSay.call(this), ?? superSay? ????, ?? ??? ?????. var superSay = Student.prototype.say ?? console.log(typeof supperSay) ??? ???? ???. , ??? ? ??? ???? ? ??? Student.prototype.say? ?????. var superSay = Student.prototype.say? ?????. ??? ??? ??? ?? People.prototype.say???. ? ?? Elevation? 166-167?????? ?????. ? ?? ???? ??? ? ??? ???? ???? ???? ???? ?? ? ????.

? ? superSay? ???? ??? ?????. var superSay = Student.prototype.say? ??? ? Student.prototype?? ??? ??? ??? ?? say ???? ?? ?????. ?? ?? ??? ???? People.prototype.say? superSay

superSay ????? ??? Student.prototype? ??????.

??? ??? ???? ????? ??? ??????