How to find item from an object with Javascript?

You must change elements to array:

var elements = [
    {
        'name' : 'test',
        'price' : '55'
    },
    {
        'name' : 'letev',
        'price': '223'
    }
];

function findElementByName(name, elementsForSearch) {
    if (name) {
        elementsForSearch.filter(function(elem){
            return elem.name === 'name';
        });
        return elementsForSearch[0];
    }
    return {};
}

alert(findElementByName('test', elements).name)

Assuming your object was an array instead of the syntax you used:

var elements = [
    {
        'name' : 'test',
        'price' : '55'
    },{
        'name' : 'letev',
        'price': '223'
    }
];

You can filter the element out like this:

searchName = 'test';
elements.filter(function(element){
    return element.name == searchName;
});

This will only return the elements that have 'test' as name.

Or as a function:

function filterByName(array, namr){
    array.filter(function(element){
        return element.name == name;
    });
}

Called like this:

array result = filterByName(elements, 'test');

In case you need to support IE 8 or lower, you can use a polyfill for Array.prototype.filter.

you can do that if your elements object was an array, i.e.

var elements = [{
        'element' : {
            'name' : 'test',
                    'price' : '55'
        },
        'element' : {
            'name' : 'letev',
                    'price': '223'
        }
    }];

var price;
for (var i=0; i  <elements.length; i++) { 
    if (elements[i].name === 'test') {
        price = elements[i].price;
        break;
    }
}

Try with:

var elements = [
  {
    'name' : 'test',
    'price' : '55'
  },
  {
    'name' : 'letev',
    'price': '223'
  }
];

var search = 'letev';
for (var i = 0; i < elements.length; i++) {
  if (elements[i].name == search) {
    alert('found!');
    break;
  }
}

Or using Array.filter:

var search = 'letev';
var output = elements.filter(function(element) {
  return element.name == search;
});

Try this

var List= (JObject)JsonConvert.DeserializeObject(jsonstring);
    var result= List["element"].Children().Select(node => node["name"]== "Test").ToList();