老師，

這個(gè)prototype里的constructor屬性有什么用處；

還有這些，

function person(){}
undefined
function student(){}
undefined
student.prototype = new person()
Object {? }
student.prototype.constructor
function person()
student.prototype.constructor = student()
undefined
student.prototype.constructor
undefined
student.prototype.constructor = student
function student()
student.prototype.constructor
function student()
var bosn = new student()
undefined
bosn instanceof person
true
person.prototype
Object { , 等 1 項(xiàng)… }
person.prototype.constructor
function person()
function one(){}
undefined
student.prototype.constructor
function student()
student.prototype.constructor = one
function one()
bosn instanceof person
true
bosn instanceof one
false
one.s = 9
9
bosn.s
undefined
student.prototype = new one()
Object {? }
bosn.s
undefined
bosn instanceof one
false
bosn instanceof person
true
student.prototype
Object {? }
bosn.z
undefined
person.z
undefined
person.prototype.z
undefined
person.prototype.z = 3
3
person.prototype.z
3
bosn.z
3
bosn.s
undefined
student.prototype
Object {? }
student.prototype.toString
function toString()
student.prototype.constructor
function one()
student.prototype = new one()
Object {? }
var v = new student()
undefined
v instanceof one
true
bosn instanceof one
false
bosn instanceof peoson
ReferenceError: peoson is not defined
bosn instanceof person
true
bosn.prototype = new one()
Object {? }
bosn instanceof person
true
bosn.prototype
Object {? }
bosn.prototype.constructor
function one()

為什么bosn instanceof person是true? 我明明把student.prototype改了 ? ? 為什么還是指向person