JsRender+ JsViews | How to $.observable().insert to object inner array-Collection of common programming errors

Sample JSON: https://gist.github.com/mekkoo/6604902

I want using $.observable().insert method to object inner array “items”. but, I looked error “Uncaught TypeError: Object # has no method ‘insert'” when method calling

pages = //Sample JSON $.ajax calling
$.observable(pages).insert(pages.length, {
    //I want this data to insert to "items" array
    "item": {
        "id":  3,
        "item_name": "Item Name 3",
        "item_desc": "Item Desc 3",
        "item_img": "http://example.com/sample.png"
    },
    "values": [
        {
            "id": 0,
            "key_id": 0,
            "value": "Value 0"
        },
        {
            "id": 1,
            "key_id": 1,
            "value": "Value 1"
        },
        {
            "id": 2,
            "key_id": 2,
            "value": "Value 2"
        }
    ]
});