Filtering JSON array using jQuery grep()

Question

I've searched many examples on this site but can't seem to fit them into my needs. I just need to filter some JSON results using grep().

Below is my JSON:

var data = { "items": [
    {
        "id":       1,
        "category": "cat1"
    },
    {        
        "id":       2,
        "category": "cat2"
    },
    {
        "id":       3,
        "category": "cat1"
    }
]}

With the example above

• how would I return all items with the category of cat1 ?
• how would I return all items with the category of cat1 and id of 3 ?

I know this isn't a great example but any help would be awesome! Thanks!

I have tried variations of the following

data.items = $.grep(data.items, function(element, index) {
    return element.id == 1;
    console.log(data.items);
});

Answer 1

var data = {
    "items": [{
        "id": 1,
        "category": "cat1"
    }, {
        "id": 2,
        "category": "cat2"
    }, {
        "id": 3,
        "category": "cat1"
    }]
};

var returnedData = $.grep(data.items, function (element, index) {
    return element.id == 1;
});


alert(returnedData[0].id + "  " + returnedData[0].category);

The returnedData is returning an array of objects, so you can access it by array index.

http://jsfiddle.net/wyfr8/913/

Answer 2

var data = {
  "items": [{
    "id": 1,
    "category": "cat1"
  }, {
    "id": 2,
    "category": "cat2"
  }, {
    "id": 3,
    "category": "cat1"
  }, {
    "id": 4,
    "category": "cat2"
  }, {
    "id": 5,
    "category": "cat1"
  }]
};
//Filters an array of numbers to include only numbers bigger then zero.
//Exact Data you want...
var returnedData = $.grep(data.items, function(element) {
  return element.category === "cat1" && element.id === 3;
}, false);
console.log(returnedData);
$('#id').text('Id is:-' + returnedData[0].id)
$('#category').text('Category is:-' + returnedData[0].category)
//Filter an array of numbers to include numbers that are not bigger than zero.
//Exact Data you don't want...
var returnedOppositeData = $.grep(data.items, function(element) {
  return element.category === "cat1";
}, true);
console.log(returnedOppositeData);

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<p id='id'></p>
<p id='category'></p>

The $.grep() method eliminates items from an array as necessary so that only remaining items carry a given search. The test is a function that is passed an array item and the index of the item within the array. Only if the test returns true will the item be in the result array.