Array of objects with some objects containing another array, need to filter it by values within the object containing an array

Sorry for the long title question didn't know how to properly formulate my question.

So this is the question, I got an array which stores objects, and within those objects there's another array with the key tags and which is an array that gets filled with tags.

Object:

var arr = new Array;

arr[0] = {
            "like": 0,
            "dislike": 0,
            "answer": "body",
            "tags" : ["offline", "facebook"],
            "comments" : []
        };

arr[1] = {
            "like": 0,
            "dislike": 0,
            "answer": "body",
            "tags" : ["school", "online"],
            "comments" : []
        };

arr[2] = {
        "like": 0,
        "dislike": 0,
        "answer": "body",
        "tags" : ["school", "offline"],
        "comments" : []
    };

The [0], [1] indexes respresent and ID, but that isn't really important here.

The problem is when I try to filter it with(I know it only tries to filter arr[0] atm but I will write a loop so it goes through all the indexes):

var toFind = "offline";

var filtered = arr[0].filter(function(el) {
  return el.tags === toFind;
});

console.log(filtered);

It says arr[0].filter is not a function, but got no idea why it thinks arr[0] should be taken into account as a function.

When I remove the [0] it gives back a blank array...

So my question is how can I get the .filter function to give back the complete object based on tags in the tags array. So that if I search for the tag "school" it gives back arr[1] and arr[2], the complete objects.

Hope I my question is crystal clear and that I provided enough information. If you guys need anymore information, feel free to ask me for it. Or if you want me to clarify things, just ask :)

Hope you guys can help me!