Arpith Siromoney 💬

Remembering what you read last

The app I’m building to share notes, Constellational, helps you keep track of what you’ve read recently. To let you re-read these posts or user pages, the navigation page displays your history as a list. It makes sense to show the last visit alone (this also keeps the list as brief as possible).

This is how I did it in React Native.

When a user or a particular post is viewed in the posts page, the url (username/postID, or just username) is added to the HistoryStore:

constructor(props, context) {
 super(props, context);
 if (this.props.username) {
     username: this.props.username,
     postURL: this.props.postURL,
     url: this.props.url

The HistoryStore keeps track of visits that look like {url: url, timestamps: [secondVisit, firstVisit]}

var HistoryStore = assign({}, EventEmitter.prototype, {
 get: function() {
   if (!_history) {
     return [];
   } else {
     var history = Object.keys(_history).map(url => _history[url]);
     var sorted = history.sort((a, b) => {
       if (a.timestamps[0] > b.timestamps[0]) return -1;
       else if (a.timestamps[0] < b.timestamps[0]) return 1;
       else return 0;
     return sorted;

Note that the get() method sorts the visits based on the most recent timestamp (the first one in the timestamps list for each visit).

This lets the NavPage display a list of the users and posts you’ve read, sorted by when you read them (without duplicates).

renderRow(row) {
 let route = {
   id: 'posts',
   username: row.username,
   postURL: row.url,
   url: row.username
  if ( route.url = row.username + '/' +;
  let onPress = () => this.props.navigator.push(route);
  let text = row.username;
  if ( text ='\n')[0];
  return <View style={styles.option}>
    <Text onPress={onPress} style={styles.text}>{text}</Text

This fixes #68.

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