Implement date filter function

README.md

@@ -153,6 +153,19 @@ const template = 'http://example.com/{section|prepend(local_)}'
 //--> http://example.com/local_news
 ```
 
+#### `date(format)`
+Formats a date according to the given date format string.
+Uses `date-and-time` under the hood, so refer to
+[their documentation](https://github.com/knowledgecode/date-and-time#formatdateobj-formatstring-utc).
+
+”Example:
+```
+const params = {updatedAfter: new Date('2020-03-19T14:08:44Z')}
+const template = 'http://example.com/all{?updatedAfter|date(DD/MM/YYYY HH:mm:ss)}'
+...
+//--> http://example.com/all?updatedAfter=20%2F03%2F2020%2019%3A43%3A11
+```
+
 #### `lower()`
 Transform the given value to lower case.
 

lib/filters/date-test.js

@@ -0,0 +1,64 @@
+import test from 'ava'
+
+import date from './date'
+
+// Tests
+
+test('should format date with provided string', (t) => {
+  const value = new Date('2020-03-18T19:59:03Z')
+  const format = 'DD.MM.YYYY'
+  const expected = '18.03.2020'
+
+  const ret = date(value, format)
+
+  t.is(ret, expected)
+})
+
+test('should format date and time with provided string', (t) => {
+  const value = new Date('2020-03-18T19:59:03Z')
+  const format = 'YYYY/MM/DD HH:mm:ss'
+  const expected = '2020/03/18 20:59:03'
+
+  const ret = date(value, format)
+
+  t.is(ret, expected)
+})
+
+test('should convert string value to date', (t) => {
+  const value = '2020-03-18T19:59:03Z'
+  const format = 'YYYY/MM/DD HH:mm:ss'
+  const expected = '2020/03/18 20:59:03'
+
+  const ret = date(value, format)
+
+  t.is(ret, expected)
+})
+
+test('should return empty string when value is not date string', (t) => {
+  const value = 'illegal'
+  const format = 'YYYY/MM/DD HH:mm:ss'
+  const expected = ''
+
+  const ret = date(value, format)
+
+  t.is(ret, expected)
+})
+
+test('should return empty string when value is not a date', (t) => {
+  const value = null
+  const format = 'YYYY/MM/DD HH:mm:ss'
+  const expected = ''
+
+  const ret = date(value, format)
+
+  t.is(ret, expected)
+})
+
+test('should return iso string when format is not a string', (t) => {
+  const value = new Date('2020-03-18T19:59:03Z')
+  const expected = '2020-03-18T19:59:03.000Z'
+
+  const ret = date(value)
+
+  t.is(ret, expected)
+})

lib/filters/date.js

@@ -0,0 +1,18 @@
+const dateTime = require('date-and-time')
+
+function date (value, format) {
+  if (typeof value === 'string') {
+    value = new Date(value)
+  }
+  if (value instanceof Date && !Number.isNaN(value.getTime())) {
+    if (typeof format === 'string' && format !== '') {
+      return dateTime.format(value, format)
+    } else {
+      return value.toISOString()
+    }
+  } else {
+    return ''
+  }
+}
+
+module.exports = date

lib/filters/index.js

@@ -1,6 +1,7 @@
 module.exports = {
   prepend: require('./prepend'),
   append: require('./append'),
+  date: require('./date'),
   upper: require('./upper'),
   lower: require('./lower'),
   wrap: require('./wrap'),

package.json

@@ -43,5 +43,8 @@
     "coveralls": "^3.0.11",
     "nyc": "^15.0.0",
     "standard": "^14.3.3"
+  },
+  "dependencies": {
+    "date-and-time": "^0.13.1"
   }
 }

tests/filterFunctions-test.js

@@ -23,3 +23,14 @@ test('should generate uri with escaped characters in filter args', (t) => {
 
   t.is(uri, expected)
 })
+
+test('should generate uri with date filter functions', (t) => {
+  const template = 'http://example.com/all{?updatedAfter|date(DD/MM/YYYY HH:mm:ss)}'
+  const params = { updatedAfter: new Date('2020-03-20T18:43:11Z') }
+  const expected = 'http://example.com/all?updatedAfter=20%2F03%2F2020%2019%3A43%3A11'
+
+  const compiled = compile(template)
+  const uri = generate(compiled, params)
+
+  t.is(uri, expected)
+})