Q:

How to retrieve object from jsonString? 

A webservice is returining jsonString.  After parsing, i'll have to bind it's value inside table. 
the easiest way to do is by finding each object inside the string. 
For eg: my string is returned in the format:
{
  "Table1": [
    {
      "ProjectId": "VS200-001---",
      "day1": "---",
      "day2": "---",
      "day3": "---",
      "day4": "---",
      "day5": "---",
      "day6": "---",
      "day7": "---",
      "day8": "---",
      "day9": "---",
      "day10": "---",
      "day11": "---",
      "day12": "---",
      "day13": "4.3",
      "day14": "2",
      "day15": "---",
      "day16": "---",
      "day17": "---",
      "day18": "---",
      "day19": "---",
      "day20": "---",
      "day21": "---",
      "day22": "---",
      "day23": "5",
      "day24": "---",
      "day25": "---",
      "day26": "---",
      "day27": "---",
      "day28": "---",
      "day29": "---",
      "day30": "---"
    },....      
  ]
} 

after parsing i got the object's. 
for(var x=0; x< _data. Length;x++)
{
  for(var dys = 0; dys< dates. Length;dys++){
  var val = "day" + (dys+1);
  tbody += _data[0] .val + "</tr>"; 
///Here exception is generating incorrect format
//but if i use here _data[0].day1 it will show the value for day1
//how to convert string to object inorder to retrieve the value

}
}

A:

When accessing an object using the key stored in a variable you need to use array notation.  Change this:
_data[0].val

To this:
_data[0][val]

From the looks of your code you also need to close the td as well.