store the input field value in json and store it in a string using javascript

I'm new to json...if anyone can help me. Here is json format. how can i store the input field value in json and store it in a string using javascript

{
"noofrooms": "4",
"guests": [
    {
        "adultcount": "1",
        "childcount": "0",
        "chidage':[]
   },
   {
    "adultcount":"1",
    "childcount":"1",
    'chidage':'[ "6"]'
   },
   {
    "adultcount":"1",
    "childcount":"2",
    'chidage':'[ "6","8"]'
   },
   {
    "adultcount":"1",
    "childcount":"2",
    'chidage':'["6", "8"]'
   }
  ],
}