Generalize String extensions to take CharSequence as receiver and parameters where applicable.

js/js.libraries/src/core/regex.kt

@@ -109,7 +109,7 @@ public class Regex(pattern: String, options: Set<RegexOption>) {
      * the given function [transform] that takes [MatchResult] and returns a string to be used as a
      * replacement for that match.
      */
-    public inline fun replace(input: CharSequence, transform: (MatchResult) -> String): String {
+    public inline fun replace(input: CharSequence, transform: (MatchResult) -> CharSequence): String {
         var match = match(input)
         if (match == null) return input.toString()
 

js/js.libraries/src/core/stringsCode.kt

@@ -43,9 +43,7 @@ public inline fun String.matches(regex : String) : Boolean {
     return result != null && result.size() > 0
 }
 
-public inline fun CharSequence.isEmpty(): Boolean = this.length() == 0
-
-public fun String.isBlank(): Boolean = length() == 0 || matches("^[\\s\\xA0]+$")
+public fun CharSequence.isBlank(): Boolean = length() == 0 || (if (this is String) this else this.toString()).matches("^[\\s\\xA0]+$")
 
 public fun String?.equals(anotherString: String?, ignoreCase: Boolean = false): Boolean =
         if (this == null)