[gatsby-medium-source] convert timestamps to ISO 8601 date string (#2099

)

* serialize big integers for gatsby-medium-source timestamps

* typos

* typo

* convert timestamps to  ISO 8601 date string

packages/gatsby-source-medium/src/gatsby-node.js

@@ -8,6 +8,19 @@ const fetch = username => {
 
 const prefix = `])}while(1);</x>`
 
+const convertTimestamps = (nextObj, prevObj, prevKey) => {
+  if (typeof nextObj === 'object') {
+    Object.keys(nextObj).map(key => convertTimestamps(nextObj[key], nextObj, key));
+  } else {
+    if (typeof nextObj === 'number' && nextObj >> 0 !== nextObj) {
+      const date = new Date(nextObj);
+      if (date.getTime() === nextObj) {
+        prevObj[prevKey] = date.toISOString().slice(0, 10);
+      }
+    }
+  }
+}
+
 const strip = payload => payload.replace(prefix, ``)
 
 exports.sourceNodes = async ({ boundActionCreators }, { username }) => {
@@ -29,6 +42,8 @@ exports.sourceNodes = async ({ boundActionCreators }, { username }) => {
 
     const resources = Array.prototype.concat(...importableResources)
     resources.map(resource => {
+      convertTimestamps(resource)
+
       const digest = crypto
         .createHash(`md5`)
         .update(JSON.stringify(resource))