function getCheckboxItems() {

    return ['100', '200']

        .map(function(selector) {

            return {

                selector: selector,

                element: document.getElementById(selector)

            }

        });

}

​

function serializeCheckboxes(elements) {

    var container = elements.reduce(function (accumulator, item) {

        accumulator[item.selector] = item.element.checked;

        return accumulator;

    }, {})

​

    localStorage.setItem('container', JSON.stringify(container));

}

​

function readCheckboxes() {

    var storage = localStorage.getItem('container'), //Your key

        container = (storage) ? JSON.parse(storage) : {};

​

    Object.keys(container).forEach(function(key) {

        var element = document.getElementById(key);

​

        if(element) {

            element.checked = container[key];

        }

    });

}

​

function save() {

    var elements = getCheckboxItems();

    serializeCheckboxes(elements);

}