store inputs/selects to sessionsStorage, if page is reloaded, set form inputs values

Form_to_sessionStorage.js

/**
* 1/ onLoad, retrieve session storage data (ALL OF IT !!! - so carefull)
* 2/ the key === input/select ID
* 3/ set the value
*/
window.onload = function () {
    if (sessionStorage) {
        for (i = 0; i < sessionStorage.length; i++) {
            var key = sessionStorage.key(i);
            var value = sessionStorage[key];
            setField(key, value);
        }
    }
};

/**
 * saveFormData
 * only inputs & selects
 */
function saveFormData() {
    // Check for LocalStorage support.
    if (sessionStorage) {
        var inputs = document.getElementsByTagName("input");
        for (i = 0; i < inputs.length; ++i) {
            elId = inputs[i].id;
            elVal = inputs[i].value;
            if (typeof elId !== "undefined") {
                storeField(elId, elVal);
            }
        }
        var selects = document.getElementsByTagName("select");
        for (i = 0; i < selects.length; ++i) {
            elId = selects[i].id;
            elVal = selects[i].value;
            if (typeof elId !== "undefined") {
                storeField(elId, elVal);
            }
        }

    }
}

/**
 * sessionStorage store action
 * @param idName
 * @param val
 */
function storeField(idName, val) {
    sessionStorage.setItem(idName, val);
}

/**
 * sessionsStorage set value field according to its ID
 * @param idName
 * @param val
 */
function setField(idName, val) {
    el = document.getElementById(idName);
    if (el !== null) {
        el.value = val;
    }
}