client context for app developement

Please find the below code read lists same way add the items

function displayLists() {
        // Get the available SharePoint lists, and then set them into
        // the context.
        lists = web.get_lists();
        context.load(lists);
        context.executeQueryAsync(onGetListsSuccess, onGetListsFail);
    }

    function onGetListsSuccess(sender, args) {
        // Success getting the lists. Set references to the list
        // elements and the list of available lists.
        var listEnumerator = lists.getEnumerator();
        var selectListBox = document.getElementById("selectlistbox");
        if (selectListBox.hasChildNodes()) {
            while (selectListBox.childNodes.length >= 1) {
                selectListBox.removeChild(selectListBox.firstChild);
            }
        }
        // Traverse the elements of the collection, and load the name of   
        // each list into the dropdown list box.
        while (listEnumerator.moveNext()) {
            var selectOption = document.createElement("option");
            selectOption.value = listEnumerator.get_current().get_title();
            selectOption.innerHTML = listEnumerator.get_current().get_title();
            selectListBox.appendChild(selectOption);
        }
    }