parseJSON - minimal implementation for parsing JSON dates from an API

src/parseJSON/benchmark.js

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+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import parseJSON from '.'
+import moment from 'moment'
+
+suite('toDate', function() {
+  benchmark('date-fns', function() {
+    return parseJSON('2014-10-25T13:46:20+00:00')
+  })
+
+  benchmark('Moment.js', function() {
+    return moment('2014-10-25T13:46:20+00:00')
+  })
+})

src/parseJSON/index.js

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+import toDate from '../toDate/index.js'
+
+/**
+ * @name parseJSON
+ * @category Common Helpers
+ * @summary Parse a JSON date string
+ *
+ * @description
+ * Converts a complete ISO date string in UTC time, the typical format for transmitting
+ * a date in JSON, to a JavaScript `Date` instance.
+ *
+ * This is a minimal implementation for converting dates retrieved from a JSON API to
+ * a `Date` instance which can be used with other functions in the `date-fns` library.
+ * The following formats are supported:
+ *
+ *     - `2000-03-15T05:20:10.123Z`: The output of `.toISOString()` and `JSON.stringify(new Date())`
+ *     - `2000-03-15T05:20:10Z`: Without milliseconds
+ *     - `2000-03-15T05:20:10+00:00`: With a zero offset, the default JSON encoded format in some other languages
+ *     - `2000-03-15T05:20:10+0000`: With a zero offset without a colon
+ *
+ * For convenience and ease of use these other input types are also supported
+ * via [toDate]{@link https://date-fns.org/docs/toDate}:
+ *
+ *     - A `Date` instance will be cloned
+ *     - A `number` will be treated as a timestamp
+ *
+ * Any other input type or invalid date strings will return an `Invalid Date`.
+ *
+ * @param {String|Number|Date} argument A fully formed ISO1806 date string to convert
+ * @returns {Date} the parsed date in the local time zone
+ */
+export default function index(argument) {
+  if (typeof argument === 'string') {
+    var parts = argument.match(
+      /(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(?:\.(\d{3}))?(?:Z|\+00:?00)/
+    )
+    if (parts) {
+      return new Date(
+        Date.UTC(
+          +parts[1],
+          parts[2] - 1,
+          +parts[3],
+          +parts[4],
+          +parts[5],
+          +parts[6],
+          +(parts[7] || 0)
+        )
+      )
+    }
+  }
+  return toDate(argument)
+}

src/parseJSON/test.js

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+import assert from 'power-assert'
+import parseJSON from '.'
+
+describe('parseJSON', function() {
+  it('parses a fully formed ISO date with Z', () => {
+    const date = '2000-03-15T05:20:10.123Z'
+    const parsedDate = parseJSON(date)
+    assert.equal(parsedDate.toISOString(), date)
+  })
+
+  it('parses a fully formed ISO date with Z without ms', () => {
+    const date = '2000-03-15T05:20:10Z'
+    const expectedDate = '2000-03-15T05:20:10.000Z'
+    const parsedDate = parseJSON(date)
+    assert.equal(parsedDate.toISOString(), expectedDate)
+  })
+
+  it('parses a fully formed ISO date with zero offset', () => {
+    const zeroOffset = '2000-03-15T05:20:10+00:00'
+    const expectedDate = '2000-03-15T05:20:10.000Z'
+    const parsedDate = parseJSON(zeroOffset)
+    assert.equal(parsedDate.toISOString(), expectedDate)
+  })
+
+  it('parses a fully formed ISO date with zero offset without colon', () => {
+    const zeroOffset = '2000-03-15T05:20:10+0000'
+    const expectedDate = '2000-03-15T05:20:10.000Z'
+    const parsedDate = parseJSON(zeroOffset)
+    assert.equal(parsedDate.toISOString(), expectedDate)
+  })
+
+  it('clones a date object', () => {
+    const date = new Date(2000, 2, 15, 5, 20, 10, 20)
+    const parsedDate = parseJSON(date)
+    assert.deepEqual(parsedDate, date)
+    assert.notEqual(parsedDate, date)
+  })
+
+  it('assumes a number is a timestamp', () => {
+    const date = new Date(2000, 2, 15, 5, 20, 10, 20)
+    const timestamp = date.getTime()
+    const parsedDate = parseJSON(timestamp)
+    assert.deepEqual(parsedDate, date)
+  })
+
+  it('returns an invalid date for anything else', () => {
+    assert.equal(parseJSON('').toString(), 'Invalid Date')
+    assert.equal(parseJSON('invalid').toString(), 'Invalid Date')
+    assert.equal(parseJSON('2020-10-10').toString(), 'Invalid Date')
+  })
+})