Beautiful Validation... Why have I never thought of this before?!

readme.md

At a certain point you just want pattern matching.

example-user.clj

(defn validates-credentials [username password]
  (let [uc (count username)
        pc (count password)]
    (match [username uc password pc]
       [(:or nil "") _ _ _]         {:error "No username given" :field "name"}
       [_ _ (:or nil "") _]         {:error "No password given" :field "pass"}
       [_ (_ :guard #(< % 3)) _ _]  {:error "Username less than 3 characters" :field "pass"}
       [_ _ _ (_ :guard #(< % 4))]  {:error "Password less than 4 characters" :field "pass"}
       [#"^([a-z0-9-_]+)$" _ _ _]   {:error "Username contains invalid characters" :field "name"}
       :else true)))

example-user.js

  var user = {
    validateCredentials: function (username, password) {
      return (
          (!(username += '') || username === '') ? { error: "No Username Given.", field: 'name' }
        : (!(username += '') || password === '') ? { error: "No Password Given.", field: 'pass' }
        : (username.length < 3)                  ? { error: "Username is less than 3 Characters.", field: 'name' }
        : (password.length < 4)                  ? { error: "Password is less than 4 Characters.", field: 'pass' }
        : (!/^([a-z0-9-_]+)$/i.test(username))   ? { error: "Username contains invalid characters.", field: 'name' }
        : false
      );
    }
  };

  var results = user.validateCredentials('Nijikokun','somepassword');
  console.log(results);

Don't disagree. But for simple cases like this pattern matching is fine. For something more sophisticated ... yes, you need something more sophisticated :)

this is pretty gouda :3