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 "]'
      }]"
}