$('.product-tab-intro').click(function () {
    console.log("product-tab-intro click");
    document.getElementById('product-tab-intro').className += " product-tab-active";
    document.getElementById('product-tab-lesson').className -= " product-tab-active";
})
$('.product-tab-lesson').click(function () {
    console.log("product-tab-intro click");
    document.getElementById('product-tab-lesson').className += " product-tab-active";
    document.getElementById('product-tab-intro').className -= " product-tab-active";
})