Querying/Searching for Values within JSON

For a web site I'm creating, I have to create a quote based on data provided as a JSON string from the server. I've been looking through this site (and various others) but still am unsure on the best way to query/search the data.

For example, I need to get the Area Name from the Area ID. I need to get the maximum age for an area and also the price for a given minimum/maximum age.

I also want to get an array of prices.

Is it best to create a Javascript object from the string using the eval method? Or should I be using jQuery.

Thanks for your help.

({"SkiPass":[{"Id":1,"Area":"Chamonix","Rates":[{"Id":1,"AgeMin":0,"AgeMax":2,"Price":2.5},{"Id":2,"AgeMin":3,"AgeMax":17,"Price":5.0},{"Id":3开发者_如何学运维,"AgeMin":18,"AgeMax":30,"Price":6.2},{"Id":4,"AgeMin":31,"AgeMax":59,"Price":7.4}]},

{"Id":2,"Area":"Megeve","Rates":[{"Id":1,"AgeMin":0,"AgeMax":2,"Price":1},{"Id":2,"AgeMin":3,"AgeMax":17,"Price":2.0},{"Id":3,"AgeMin":18,"AgeMax":30,"Price":2.2},{"Id":4,"AgeMin":31,"AgeMax":59,"Price":4.4}]},

{"Id":3,"Area":"Verbier","Rates":[{"Id":1,"AgeMin":0,"AgeMax":2,"Price":1.5},{"Id":2,"AgeMin":3,"AgeMax":17,"Price":3.0},{"Id":3,"AgeMin":18,"AgeMax":30,"Price":4.2},{"Id":4,"AgeMin":31,"AgeMax":59,"Price":5.4}]}]})

Create a JavaScript object from the string, most definitely, but do it with legitimate JSON parsing facilities and not "eval()". You could use jQuery, but there are other solutions, such as the JSON tools available from json.org, which are small and simple.

Once it's a JavaScript object, well then your needs should guide you as to whether some query solution is necessary, or instead that it's just a simple matter of programming.

I think the best method is jLinq: http://hugoware.net/Projects/jLinq it's like doing a SQL query on JSON. It doesn't needs jQuery. I use it, and it's great.

Create the object from the JSON string using JSON.parse() or jQuery.parseJSON() if you are already using jQuery -- or just pass it as from the server side as JSON.

You can then iterate through the object to find the record you want. Or, you can use build your objects so that you can naturally grab data from them.

FloatLeft - as Dan points out, your task would be much easier if you could use XPath but there is no need to re-write your data in XML format. With DefiantJS (http://defiantjs.com) you can now query JSON structure with XPath expressions.

DefiantJS extends the global object JSON with the method "search", which enables XPath queries and returns an array with the matches (empty array if no matches were found). The returned array is equipped with aggregate functions as well; one of these "sortDesc".

Check out this working fiddle;
http://jsfiddle.net/hbi99/H3PR3/

var data = {
  "SkiPass": [
      ...
      {
        "Id": 3,
        "Area": "Verbier",
        "Rates": [
           { "Id": 1,  "AgeMin": 0,  "AgeMax": 2,  "Price": 1.5 },
           { "Id": 2,  "AgeMin": 3,  "AgeMax": 17, "Price": 3   },
           { "Id": 3,  "AgeMin": 18, "AgeMax": 30, "Price": 4.2 },
           { "Id": 4,  "AgeMin": 31, "AgeMax": 59, "Price": 5.4 }
        ]
     }
  ]
},
res1 = JSON.search( data, '//SkiPass[Id=3]/Area' ),
res2 = JSON.search( data, '//*[Area and Id=3]/Rates' )
           .sortDesc('AgeMax');  // <-- sorting descending by the value of "AgeMax"

document.getElementById('name').innerHTML = res1;

document.getElementById('max_age').innerHTML = res2[0].AgeMax;
document.getElementById('price').innerHTML = res2[0].Price;