form serialize javascript (no framework)

function serialize (form) {
    if (!form || form.nodeName !== "FORM") {
            return;
    }
    var i, j, q = [];
    for (i = form.elements.length - 1; i >= 0; i = i - 1) {
        if (form.elements[i].name === "") {
            continue;
        }
        switch (form.elements[i].nodeName) {
            case 'INPUT':
                switch (form.elements[i].type) {
                    case 'text':
                    case 'tel':
                    case 'email':
                    case 'hidden':
                    case 'password':
                    case 'button':
                    case 'reset':
                    case 'submit':
                        q.push(form.elements[i].name + "=" + encodeURIComponent(form.elements[i].value));
                        break;
                    case 'checkbox':
                    case 'radio':
                        if (form.elements[i].checked) {
                                q.push(form.elements[i].name + "=" + encodeURIComponent(form.elements[i].value));
                        }                                               
                        break;
                }
                break;
                case 'file':
                break; 
            case 'TEXTAREA':
                    q.push(form.elements[i].name + "=" + encodeURIComponent(form.elements[i].value));
                    break;
            case 'SELECT':
                switch (form.elements[i].type) {
                    case 'select-one':
                        q.push(form.elements[i].name + "=" + encodeURIComponent(form.elements[i].value));
                        break;
                    case 'select-multiple':
                        for (j = form.elements[i].options.length - 1; j >= 0; j = j - 1) {
                            if (form.elements[i].options[j].selected) {
                                    q.push(form.elements[i].name + "=" + encodeURIComponent(form.elements[i].options[j].value));