On Oct 14, 2013, at 5:54 PM, Andrea Giammarchi wrote: > Allen my confusion is with o4 ... what happens once you re-set/assign its > `__proto__` there? > > Is it just a normal property so new value will be set ? > Is it a magic inherited thing (it shouldn't) that will change the o4 > prototype chain ?
JSON.parse is just a function that builds up simple (inheriting from Object.prototype) objects using [[DefineOwnProperty]] See http://people.mozilla.org/~jorendorff/es6-draft.html#sec-24.3.2 step 3.a.iv.3.a. So if the JSON object text contains a "__proto__" property key, the object that is created with have a "__proto__" own data property. If it doesn't then the Annex B2.2.1 Object.prototype__proto__ property is inherited. No magic involved. Allen > ... > Assuming that Annex B.2.2.1 and B.3.1 are implemented: here are the cases of > interest: > > let o1 = {__proto__: p}; // o1 inherits from p > let o2 = {"__proto__": p}; // o2 inherits from p > let o3 = {["__proto__"]: p};// o3 inherits from Object.prototype, has own > data property "__proto__" whose value is p. > let o4 = JSON.parse('{"__proto__": "value"}'); > //o4 inherits from Object.prototype, has own data property "__proto__" > whose value is "value" > > //assuming that Object.prototype.__proto__ has not been tamper with: > let o5 = new Object; > o5.__proto__ = p ; //o5 inherits from p > > let o6 =new Object; > o6["__proto__"] = p; //o6 inherits from p > > Allen >
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