JS: add Util::pluralize, also add tests for Util::capitalize

javascript/ql/src/semmle/javascript/Util.qll

@@ -11,3 +11,16 @@ bindingset[s]
 string capitalize(string s) {
   result = s.charAt(0).toUpperCase() + s.suffix(1)
 }
+
+ /**
+  * Gets the pluralization for `n` occurrences of `noun`.
+  *
+  * For example, the pluralization of `"function"` for `n = 2` is `"functions"`.
+  */
+bindingset[noun, n]
+string pluralize(string noun, int n) {
+  if n = 1 then
+    result = noun
+  else
+    result = noun + "s"
+}

javascript/ql/test/library-tests/Util/capitalize.expected

@@ -0,0 +1 @@
+| X | X | Xx | XX | Xx | XX |

javascript/ql/test/library-tests/Util/capitalize.ql

@@ -0,0 +1,3 @@
+import semmle.javascript.Util
+
+select capitalize("x"), capitalize("X"), capitalize("xx"), capitalize("XX"), capitalize("Xx"), capitalize("xX")

javascript/ql/test/library-tests/Util/pluralize.expected

@@ -0,0 +1 @@
+| xs | x | xs | xs |

javascript/ql/test/library-tests/Util/pluralize.ql

@@ -0,0 +1,3 @@
+import semmle.javascript.Util
+
+select pluralize("x", 0), pluralize("x", 1), pluralize("x", 2), pluralize("x", -1)

javascript/ql/test/library-tests/Util/tst.js

@@ -0,0 +1 @@
+// used by qltest to identify the language