blank?

user> (clojure.string/blank? nil)
true

user> (clojure.string/blank? "")
true

user> (clojure.string/blank? "   ")
true

user> (clojure.string/blank? " a ")
false

user> (clojure.string/blank? false)
true

user> (clojure.string/blank? "\n")
true

;; A way to remove blanks from a string.
(def astr "This contains  blanks \n \t \r and other whitespace")
(->> astr 
     (#(clojure.string/split % #"\s")) 
     (remove clojure.string/blank?) 
     (clojure.string/join " "))

;;=> "This contains blanks and other whitespace"

;; Of course the task can be better performed other ways.
;; The goal here is just to show how blank? works.
(clojure.string/replace (clojure.string/trim astr) #"\s{2,}" " ")

;; The list of the 25 whitespace chars in UTF-16. Using the \uNNNN hex code
;; when another representation is not available or not printable.
;; \u0020 is the common white space, AKA " " or '\space' as a single char.

(require '[clojure.string :as s])

(s/blank? "\t \n \u000b \f \r \u001c \u001d \u001e \u001f") ;; true
(s/blank? "\u0020 \u1680 \u2000 \u2001 \u2002 \u2003") ;; true
(s/blank? "\u2004 \u2005 \u2006 \u2008 \u2009") ;; true
(s/blank? "\u200a \u2028 \u2029 \u205f \u3000") ;; true