feat: add convert function

src/convert.ts

@@ -0,0 +1,13 @@
+import export_ from './export'
+import import_ from './import'
+
+/**
+ * Convert a thing from one format to another.
+ *
+ * @param thing The thing to convert as a string
+ * @param from The current format of the thing as a MIME type e.g. `text/markdown`
+ * @param to The desired format for the thing as a MIME type e.g. `text/html`
+ */
+export default function convert (thing: string, from: string= 'application/ld+json', to: string= 'application/ld+json'): string {
+  return export_(import_(thing, from), to)
+}

src/export.ts

@@ -21,8 +21,9 @@ export default function export_ (thing: Thing, format: string= 'application/ld+j
  * @param thing The thing to be exported
  */
 export function exportJsonLd (thing: Thing): string {
-  const obj = exportObject(thing)
-  obj['@context'] = 'https://stencila.github.io/schema/context.jsonld'
+  const obj = Object.assign({
+    '@context': 'https://stencila.github.io/schema/context.jsonld'
+  }, exportObject(thing))
   return JSON.stringify(obj)
 }
 

tests/convert.test.ts

@@ -0,0 +1,8 @@
+import convert from '../src/convert'
+
+test('convert:Thing', () => {
+  const jsonld = '{"@context":"https://stencila.github.io/schema/context.jsonld","type":"Thing","name":"Thing1"}'
+  expect(convert(jsonld, 'application/ld+json', 'application/ld+json')).toEqual(jsonld)
+  expect(() => convert('blah', 'foo/bar')).toThrow(/^Unhandled import format: foo\/bar/)
+  expect(() => convert('{"type":"Person"}', undefined, 'foo/bar')).toThrow(/^Unhandled export format: foo\/bar/)
+})