Adding data to array with JSON field

Question

I'm having problem with my data property.

data: function() {
        return {
            conversations: 
            [

            ]
        }
}

When I make a request to server i get response with data. I store these items in response.data.conversations. It has property named response.data.conversations[].messages which is saved in JSON notation and stores multiple items. I don't know how to ADD new items to that field.

That's what I have tried:

for(var i=0; i<response.data.conversations.length; i++) {
    for(var j=0; j<this.conversations.length; j++) {
        if(response.data.conversations[i].conversation_id == this.conversations[j].conversation_id) {
            var obj = JSON.parse(this.conversations[j].messages);
            obj.push(JSON.parse(response.data.conversations[i].messages));
            this.conversations[j].messages = JSON.stringify(obj); 
        }
    }
 }