feat(is-boolean): add isBoolean helper function

this also checks for booleans created using the Boolean constructor. We implement this for completeness and to have the same logic as isString() and isNumber()

Author: michaelwittwer

src/helper/is-boolean.function.ts

@@ -0,0 +1,9 @@
+import { getTag } from './get-tag.function'
+import { Tag } from './tag.enum'
+
+/**
+ * @return Returns true for any value where typeof equals 'string' or an object created with String constructor
+ */
+export function isBoolean(value: any): boolean {
+  return typeof value === 'boolean' || getTag(value) === Tag.BOOLEAN
+}

src/helper/is-boolean.spec.ts

@@ -0,0 +1,19 @@
+import { isBoolean } from './is-boolean.function'
+
+describe('is boolean', () => {
+  it('should be a boolean', () => {
+    expect(isBoolean(true)).toBeTruthy()
+    expect(isBoolean(false)).toBeTruthy()
+    // tslint:disable:no-construct
+    expect(isBoolean(new Boolean(1))).toBeTruthy()
+    expect(isBoolean(new Boolean(0))).toBeTruthy()
+  })
+
+  it('should not be a boolean', () => {
+    expect(isBoolean(0)).toBeFalsy()
+    expect(isBoolean(1)).toBeFalsy()
+    expect(isBoolean('a')).toBeFalsy()
+    expect(isBoolean({})).toBeFalsy()
+    expect(isBoolean([])).toBeFalsy()
+  })
+})

src/helper/tag.enum.ts

@@ -3,4 +3,5 @@ export enum Tag {
   OBJECT = '[object Object]',
   STRING = '[object String]',
   NUMBER = '[object Number]',
+  BOOLEAN = '[object Boolean]',
 }

src/mapper/util.spec.ts

@@ -118,6 +118,8 @@ describe('Util', () => {
     it('detects bool', () => {
       expect(detectType(true)).toBe('BOOL')
       expect(detectType(false)).toBe('BOOL')
+      // tslint:disable-next-line:no-construct
+      expect(detectType(new Boolean(1))).toBe('BOOL')
     })
     it('detects collection', () => {
       expect(detectType(new Set(['a']))).toBe('SS')

src/mapper/util.ts

@@ -2,6 +2,7 @@
  * @module mapper
  */
 import { PropertyMetadata } from '../decorator/metadata/property-metadata.model'
+import { isBoolean } from '../helper/is-boolean.function'
 import { isNumber } from '../helper/is-number.function'
 import { isString } from '../helper/is-string.function'
 import { ModelConstructor } from '../model/model-constructor'
@@ -155,7 +156,7 @@ export function detectType(value: any): AttributeType {
     return 'B'
   } else if (value === null) {
     return 'NULL'
-  } else if (typeof value === 'boolean') {
+  } else if (isBoolean(value)) {
     return 'BOOL'
   } else if (isCollection(value)) {
     return detectCollectionTypeFromValue(value)
@@ -181,19 +182,16 @@ export function typeOf(propertyValue: any, propertyPath?: string | null): Attrib
     return Map
   } else if (isBinary(propertyValue)) {
     return Binary
-  } else {
-    switch (typeof propertyValue) {
-      case 'string':
-        return String
-      case 'number':
-        return Number
-      case 'boolean':
-        return Boolean
-      case 'undefined':
-        return UndefinedType
-      case 'object':
-        return Object
-    }
+  } else if (isString(propertyValue)) {
+    return String
+  } else if (isNumber(propertyValue)) {
+    return Number
+  } else if (isBoolean(propertyValue)) {
+    return Boolean
+  } else if (typeof propertyValue === 'undefined') {
+    return UndefinedType
+  } else if (typeof propertyValue === 'object') {
+    return Object
   }
 
   throw new Error(messageWithPath(propertyPath, `typeof data ${propertyValue} could not be detected`))