other components... (2)

src/validation/duplicate.ts

@@ -0,0 +1,23 @@
+type t = string | number
+type fn = () => t[]
+
+export function duplicate(matches: t[] | fn, ignoreCase: boolean): any {
+  if (Array.isArray(matches)) return factory(matches, ignoreCase)
+
+  return (value: any) => {
+    let cb = factory(matches(), ignoreCase)
+    return cb(value)
+  }
+}
+
+function factory(values: t[], ignoreCase: boolean): any {
+  return (value: any) => {
+    if (value === undefined || value === null || values.length === 0)
+      return true
+    else {
+      let flags = ignoreCase ? 'i' : ''
+      let exp = new RegExp(`^(${value})$`, flags)
+      return values.find(o => exp.test(o.toString())) === undefined
+    }
+  }
+}