Add String.isEmpty and String.capitalize

Author: DZakh

lib/es6/Stdlib_String.js

@@ -25,9 +25,23 @@ function searchOpt(s, re) {
 
 }
 
+function isEmpty(s) {
+  return s.length === 0;
+}
+
+function capitalize(s) {
+  if (s.length === 0) {
+    return s;
+  } else {
+    return s[0].toUpperCase() + s.slice(1);
+  }
+}
+
 export {
   indexOfOpt,
   lastIndexOfOpt,
   searchOpt,
+  isEmpty,
+  capitalize,
 }
 /* No side effect */

lib/js/Stdlib_String.js

@@ -25,7 +25,21 @@ function searchOpt(s, re) {
 
 }
 
+function isEmpty(s) {
+  return s.length === 0;
+}
+
+function capitalize(s) {
+  if (s.length === 0) {
+    return s;
+  } else {
+    return s[0].toUpperCase() + s.slice(1);
+  }
+}
+
 exports.indexOfOpt = indexOfOpt;
 exports.lastIndexOfOpt = lastIndexOfOpt;
 exports.searchOpt = searchOpt;
+exports.isEmpty = isEmpty;
+exports.capitalize = capitalize;
 /* No side effect */

runtime/Stdlib_String.res

@@ -170,4 +170,13 @@ external splitByRegExpAtMost: (string, Stdlib_RegExp.t, ~limit: int) => array<op
 
 @send external localeCompare: (string, string) => float = "localeCompare"
 
+let isEmpty = s => length(s) == 0
+
+let capitalize = s =>
+  if isEmpty(s) {
+    s
+  } else {
+    toUpperCase(getUnsafe(s, 0)) ++ sliceToEnd(s, ~start=1)
+  }
+
 external ignore: string => unit = "%ignore"

runtime/Stdlib_String.resi

@@ -793,6 +793,36 @@ String.searchOpt("no numbers", %re("/\d+/")) == None
 */
 let searchOpt: (string, Stdlib_RegExp.t) => option<int>
 
+/**
+`isEmpty(str)` returns `true` if the string is empty (has zero length), 
+`false` otherwise.
+
+## Examples
+
+```rescript
+String.isEmpty("") == true
+String.isEmpty("hello") == false
+String.isEmpty("  ") == true
+```
+*/
+let isEmpty: string => bool
+
+/**
+`capitalize(str)` returns a new string with the first character converted to 
+uppercase and the remaining characters unchanged. If the string is empty, 
+returns the empty string.
+
+## Examples
+
+```rescript
+String.capitalize("hello") == "Hello"
+String.capitalize("HELLO") == "HELLO"
+String.capitalize("hello world") == "Hello world"
+String.capitalize("") == ""
+```
+*/
+let capitalize: string => string
+
 /**
 `slice(str, ~start, ~end)` returns the substring of `str` starting at
 character `start` up to but not including `end`.