Function - Javascript Scope and local variables

Questions

I m really not sure if this is possible in Javascript. Here s my function:

var tree = function(name, callback) {
  if (this.name) {
    this.name.push(name)
    print(this.name)
  } else {
    this.name = []
  }
  callback()
}

I d like to use it as follows and print out the hierarchy:

tree("john", function() {
  tree("geoff", function() {
    tree("peter", function() {
      tree("richard", function() {
      })
    })
  })
  tree("dave", function() {
  })
})

Here s the desired output:

// [ john ]
// [ john ,  geoff ]
// [ john ,  geoff ,  peter ]
// [ john ,  geoff ,  peter ,  richard ]
// [ john ,  dave ]

but unfortunately I m getting

// [ john ,  geoff ,  peter ,  richard ,  dave ]

for the last function call. Is there a way to get the desired outcome?

Kind regards

Adam Groves

Answers

The reason why the last line is printing all the names is because this.names is never removing the names that are being added to it. You re just appending names onto it. So when the function call is made

callback()  

with the value

function() {
  tree("richard", function() {
})  

 this.names = [ john ,  geoff ,  peter ]   and after the call   this.names = [ john ,  geoff ,  peter ,  richard ]  . So now when you call  

tree("dave", function() {
});

this.names is still [ john , geoff , peter , richard ] .

Try the following instead, and notice I changed this.name to this.names to make is easier to read.

var tree = function(name, callback) {
  if (!this.names) {
    this.names = [];
  }
  this.names.push(name);
  print(this.names);
  callback();
  this.names.pop();
}  

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/2075301/javascript-scope-and-local-variables

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