Adding omitValues

README.md

@@ -29,7 +29,10 @@ npm i --save json-map-transform
 
 **Transform:** Is a callback that can be used to transform the current property. It receives two parameters: (property, originalObject).
 
-**Default:** In case a path does not exists in the input object, the default value will be uses.
+**Default:** In case a path does not exists in the input object or the value returned by transform is undefined, the default value will be used.
+
+**OmitValues:** Sometimes it is necessary to ignore values on the transformation (ex: undefined, empty string or other values depending on a business rule). With the omitValues, it is possible to define an array of values that should be ignored on the transformation. The output object will not the associated key.
+
 
 Template example:
 
@@ -41,6 +44,7 @@ const template = {
 	},
 	label: {
 		path: ['category', 'categories'],
+		omitValues: ['', undefined, 'ERROR']
 	},
 	vendor: {
 		path: 'meta.vendor',

lib/jsonMapTransform.js

@@ -5,9 +5,14 @@ const has = require('./utils/objectHandler').has;
 const setObjectValue = (template, key, value, json, transformedJson) => {
 	const defaultValue = template[key].default;
 	const transform = template[key].transform;
-	const transformedValue = transform ? transform(value, json) : value;
+	const omitValues = template[key].omitValues || [];
+	const transformedValue = (transform ? transform(value, json) : value) || defaultValue;
 
-	return set(Object.assign({}, transformedJson), key, transformedValue || defaultValue);
+	if(omitValues.indexOf(transformedValue) == -1) {
+		return set(Object.assign({}, transformedJson), key, transformedValue);
+	}
+
+	return transformedJson;
 };
 
 const transformJson = (json, template, afterTransform) => {

test/jsonMapTransform.test.js

@@ -73,6 +73,34 @@ test('ignores invalid path', () => {
 	expect(convertedJson.vendor).toBe('Author name');
 });
 
+test('Omits undefined value', () => {
+	const convertedJson = transform(product1, Object.assign({}, template, {
+		wrongProperty: {
+			path: 'unexistingPath',
+			omitValues: [undefined],
+		}
+	}));
+
+	expect(convertedJson).not.toHaveProperty('wrongProperty');
+	expect(convertedJson.title).toBe('HELLO WORLD');
+	expect(convertedJson.label).toBe('books');
+	expect(convertedJson.vendor).toBe('Author name');
+});
+
+test('Omits undefined value returned by transform', () => {
+	const convertedJson = transform(product1, Object.assign({}, template, {
+		title: {
+			path: 'name',
+			omitValues: ['ERROR', '', undefined],
+			transform: () => 'ERROR'
+		}
+	}));
+
+	expect(convertedJson).not.toHaveProperty('title');
+	expect(convertedJson.label).toBe('books');
+	expect(convertedJson.vendor).toBe('Author name');
+});
+
 test('executes transformation callback for a single object', () => {
 	const convertedJson = transform(product1, template, afterTransform);