遍历Javascript对象属性的方法

$ node
> var myobj = {k1: "p1", k2: 'p2'}

> for (var key in myobj) {
... console.log(key);
... console.log(myobj.key);
... console.log(myobj[key]);
... }
k1
undefined
p1
k2
undefined
p2
> myobj.k1
'p1'

> var ak = 'k4'
undefined
> myobj.ak = 'p4'
'p4'
> myobj
{ k1: 'p1',
  k2: 'p2',
  ak: 'p4' }
> myobj[ak] = 'p4'
'p4'
> myobj
{ k1: 'p1',
  k2: 'p2',
  ak: 'p4',
  k4: 'p4' }

> myobj[nk] = 'p5'
ReferenceError: nk is not defined
    at repl:1:8
    at REPLServer.self.eval (repl.js:110:21)
    ...
> myobj['nk'] = 'p5'
'p5'
> myobj
{ k1: 'p1',
  k2: 'p2',
  ak: 'p4',
  k4: 'p4',
  nk: 'p5' }