Merge pull request #43 from Gontrum/40-add-jsonMapper-into-mappers

#40 Add jsonMapper into mappers

Author: Siemienik

README.md

@@ -128,6 +128,7 @@ This is `type` related configuration, for more information please study examples
 |-----|-----------
 |upperCaseMapper|Transforms string to upper case
 |lowerCaseMapper|Transforms string to lower case
+|jsonMapper|Transforms a json string to a TJsonResponse or to null if parsing was not possible
 |isEmpty|Examines if input is empty
 |isFilled|Examines if input is not empty
 

src/mappers/index.ts

@@ -6,3 +6,4 @@ export { upperCaseMapper } from './upperCaseMapper';
 export { lowerCaseMapper } from './lowerCaseMapper';
 export { isEmpty } from './isEmpty';
 export { isFilled } from './isFilled';
+export { jsonMapper } from './jsonMapper';

src/mappers/jsonMapper.ts

@@ -0,0 +1,11 @@
+import { ValueMapper } from '../abstracts/ValueMapper';
+
+type JsonMapper = <TJsonResult>(value: string) => TJsonResult | null;
+
+export const jsonMapper: JsonMapper = <TJsonResult extends any>(value: string): TJsonResult | null => {
+    try {
+        return JSON.parse(value)
+    } catch (e) {
+        return null
+    }
+}

tests/unit/mappers/stringMapper.test.ts

@@ -1,5 +1,11 @@
 import * as chai from 'chai';
-import { isEmpty, isFilled, lowerCaseMapper, upperCaseMapper } from '../../../src/mappers';
+import {
+    isEmpty,
+    isFilled,
+    jsonMapper,
+    lowerCaseMapper,
+    upperCaseMapper
+} from '../../../src/mappers';
 import { stringMapper } from '../../../src/mappers/stringMapper';
 
 describe('Mappers, unit tests', () => {
@@ -60,6 +66,29 @@ describe('Mappers, unit tests', () => {
       });
   });
 
+  describe('jsonMapper', () => {
+    const dataProvider = [
+        { inValue: '', expectedResult: null },
+        { inValue: null, expectedResult: null },
+        { inValue: ' ', expectedResult: null },
+        { inValue: 'asd', expectedResult: null },
+        { inValue: 'null', expectedResult: null },
+        { inValue: 'false', expectedResult: false },
+        { inValue: 'true', expectedResult: true },
+        { inValue: '0', expectedResult: 0},
+        { inValue: '1', expectedResult: 1},
+        { inValue: '"string"', expectedResult: 'string'},
+        { inValue: '\'string\'', expectedResult: null},
+        { inValue: '{"a":1}', expectedResult: {a:1}},
+        { inValue: '{"a":[1]}', expectedResult: {a:[1]}},
+      ]
+      dataProvider.forEach(({inValue, expectedResult}) => {
+          it(`jsonMapper for input "${inValue}" SHOULD return "${JSON.stringify(expectedResult)}"`, () => {
+              chai.expect(jsonMapper(inValue as string)).is.eql(expectedResult);
+          });
+      });
+  });
+
   describe('isEmpty', () => {
     const dataProvider = [
         { inValue: '', expectedResult: true },