如何在最小化重复的同时使用客户端和服务器端验证？

I am currently validating user input on server side (PHP). The client side sends XMLHttpRequest calls and marks invalid fields with red borders. Everything else is great except that I think it takes too long for the client to make a request and then notice that he filled something wrong. I think I should place some JavaScript validations as well so that the client does not need to wait for the request to finish.I am currently validating user input on server