updating/adding data to json file using angularjs and nodejs

I used the code which has already been asked in one of the question. Having said that, i wanted to update the json file which is empty initially with only curly braces using the nodejs and angularjs code. When i enter in the input fields and click on submit, the data should get updated in json file. There is something wrong in my controller code. please help!! controller

[server side code][2]

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via Arvind